CoCoRaHS's 20th Anniversary - June 2018


The Community Collaborative Rain, Hail and Snow Network (CoCoRaHS) began on June 17, 1998.  With a few observers along Colorado's Front Range, we had no idea that the network would become what it is today, with over 20,000 active observers in the United States, Canada, Puerto Rico, the U.S.Virgin Islands and the Bahamas.  Please join us below for a series of messages that will be running during May and June 2018 as part of our 20 year Anniversary Celebration.

CoCoRaHS - Celebrating 20 Years: The beginnings


During the summer of 1997, the Colorado Climate Center initiated a small project to test the feasibility of equipping volunteers with foil-covered Styrofoam pads in an effort to improve data resources related to Colorado hailstorms.   A high school student quipped “By the time it hails, we will have forgotten what you asked us to do.  Wouldn’t it be better to have volunteers involved in something that can give them something to do more often?”  Then on the afternoon of July 27, 1997, it began to rain along the west side of Fort Collins, Colorado.  The following day the rain intensity grew – again mostly on the west edge of the city.  Just five miles to the east only a light rain fell.  As the afternoon turned to night the west side of town was engulfed in a deluge that did not let up. Spring Creek, usually a small stream barely four feet wide, became a raging torrent overflowing its banks as it flowed eastward following it's natural path to lower elevation. More than 13 inches of rain fell (almost the yearly average) from this storm on the west side of town, resulting in a devastating flash flood that claimed five lives that night.  No one reported the heavy rain to the National Weather Service office.  The opportunity to provide early warning of this flood was missed.
Fast forward to spring of 1998.  Thanks to a small grant from the Colorado Office of Emergency Management and help from Fort Collins water and storm water utilities, a project was envisioned to engage students and families from across Fort Collins in measuring and reporting precipitation from summer storms.  The name “Colorado Collaborative Rain and Hail Study” (CoCoRaHS) was coined.  Three high school students were enlisted to help == each with different skills and talents.  Daphne from Poudre High School was in charge of volunteer recruiting and training. She successfully found at least one family from every school in the district (40 at the time) to help.  Luke from Fort Collins High School was interested in web development and got to work designing webpages for volunteers to access to enter their daily rainfall reports.  Tom, from Rocky Mountain High School, was the big thinker of the group and envisioned a way to store, display and map all the data each day so volunteers could quickly see how their rainfall measurement compared to others in and near Fort Collins.  The team didn’t get much of their regular school work done that spring, but they worked feverishly on CoCoRaHS. Then serendipity showed up in the form of a public service announcement.  It aired on a local “oldies” station playing music from the 1940s and 50s.  Many retirees responded by volunteering to help measure rain and hail. As summer approached the building blocks for CoCoRaHS were in place.

Nolan and the team of students held a series of public seminars and a rain and hail measurement training session.  The community responded enthusiastically.  On June 17th, 1998 the students flipped the switch and turned on the first version of the CoCoRaHS website – and it worked!!!  Several dozen reports were successfully submitted and mapped.  CoCoRaHS was born. (Watch the video)  

In the coming weeks, we’ll tell other parts of the story of CoCoRaHS.  Please join us as we celebrate over the next two months!

CoCoRaHS - Celebrating 20 Years: The First Five Years

The first five years of CoCoRaHS were exciting but chaotic, as the project gradually gained momentum. Financial and personnel resources were few, but energy and commitment from our volunteers was exceptionally high and motivational.  Our high school students that got the project started all graduated and moved on.  Fortunately, one of our adult volunteers with computer programming experience stepped forward to help maintain the website. Other volunteers helped manage phone calls and other essential duties.

The first winter set the tone.  Our initial intent was to stand down the project for the winter months and start again in spring (1999).  However, many volunteers protested.  They wanted to measure and report snow, too.  After some consideration, we decided to give it a try.  We organized several well-attended training session on how to measure and report snow.  We also adjusted our name a bit – upgrading CoCoRaHS to be the “Colorado Collaborative Rain, Hail and Snow network.  Growth and expansion began slowly in the nearby communities of Loveland and Greeley.  A stormy week and a regional flood in late April 1999 showed clearly the value of a detailed local rain gauge network. Data credibility grew.

In an effort to thank and motivate volunteers, we began organizing educational opportunities such as evening seminars and weekend field trips.  Kids, families and seniors all participated with keen interest.  We partnered with a research radar facility nearby that was exploring remote sensing of hail.  We began doing “hail pad parties” as a way of involving volunteers in project logistics.

While attending a meteorological conference out of state, Nolan stumbled upon a flyer lying on a table.  This flyer described a new program on geoscience education at the National Science Foundation.  It seemed perfect for CoCoRaHS.   Within a few months, we wrote a proposal that was promptly funded – linking CoCoRaHS to a major thunderstorm research project scheduled for the summer of 2000.  We were presented with a unique opportunity to support the research mission of the Severe Thunderstorm Electrification and Precipitation Study (STEPS).  This NSF funding supported hiring several high school and college students to help with volunteer recruiting, training and data collection.  We helped organize public events to meet project scientists, and we held a field trip to Goodland, Kansas to see the research aircraft and National Weather Service office there.

After so much enthusiasm and growth in 1999 – 2000, weather patterns changed. Storms gave way to drought.  Recruiting volunteers got harder and harder. A common response to our invitation to join CoCoRaHS was “Who needs a rain gauge.  All I’d ever measure is dust.”  But as the extreme drought of 2002 unfolded, some volunteers became active spokespeople for local drought awareness and community water conservation. A broader interest in CoCoRaHS developed leading to sponsorship from several Colorado water utilities. Partnerships developed almost spontaneously with Extension Offices, USDA County Service Centers and Conservation Districts leading to dramatic growth particularly in rural Colorado. 

By 2003 CoCoRaHS had expanded to much of the State – and just in a nick of time.  While facing prospects of multiyear extreme drought that March, a storm system took shape over the West headed towards Colorado. Copious moisture from the Gulf of Mexico streamed northwestward towards Colorado feeding into the storm.  Thanks to excellent weather forecasts and the ability to contact volunteers efficiently by email, warnings of several feet of wet snow were communicated along with instructions on how to measure huge snow.  The storm materialized, and exceptional snowfall and water content data were collected that were immediately valuable in storm documentation, engineering applications (many roofs collapsed), and research.

In just five years, CoCoRaHS grew from a local experiment to a year-round source of reliable statewide data. The partnerships that had been forged were also aiding the overall outreach and climate monitoring mission of the Colorado Climate Center.  Other states were taking notice.

CoCoRaHS - Celebrating 20 Years: CoCoRaHS spreads across the United States

From the very beginning of CoCoRaHS in 1998, the radar meteorology research group in the Department of Atmospheric Science at Colorado State University had watched with interest.  Data collected by volunteers with plastic rain gauges and foil-wrapped Styrofoam pads repeatedly proved useful in the research efforts of the CSU CHILL Radar team.  In an effort to help CoCoRaHS, one of their scientists, Dr. Rob Cifelli, helped draft a proposal to the National Science Foundation to expand CoCoRaHS from Colorado into portions of Kansas, Nebraska and Wyoming.  Much to our surprise and amazement, the proposal was funded in 2003, providing support to hire a small staff -- a project coordinator and a Web developer. Within a year, a new and greatly advanced website was up and running and volunteers were signing up in our neighboring states.  National Weather Service offices and State Climatologists from these adjacent states were immediately eager to get involved.  Nebraska took special ownership in the idea and invited Nolan Doesken to speak to the Nebraska Natural Resource Districts and provide detailed training in precipitation measurement procedures.  Soon after, the Nebraska Rainfall Analysis Information Network was launched – affectionately named NeRAIN (pronounced “Any Rain”).  The number of active volunteers quickly grew from a few hundred in 2003 to over 2,000 by the summer of 2004.

The new website provided nearly instantaneous access to state and county maps of precipitation data allowing both participants and other internet users to view and access local precipitation data for every day of the year.  An impressive “Administrative” portal helped volunteer leaders to efficiently assign station names and numbers to each new volunteer and also track and communicate with these participants.  

In 2004 a new CoCoRaHS national coordinator was hired.  That was Henry Reges, a meteorologist with the American Meteorological Society with a business management background, and with many professional connections. During the first month on the job, he began building a national vision for the project. This included the revised name “Community Collaborative Rain, Hail and Snow” network and a sharp new logo.  Julian Turner, who served both as web developer and volunteer support leader refined the website and added creative artistic touches.  More training materials were also added making the website a hub both for volunteer data collectors but also for a growing number of users interested in precipitation.  

As CoCoRaHS matured into a professional-looking young organization, other states took interest and began asking to join.  New Mexico rolled out CoCoRaHS in 2005 with great success. At about this same time, Chad Gimmestad, a local meteorologist with the National Weather Service in Boulder developed a capability for CoCoRaHS hail and heavy rain reports to be almost instantly communicated to National Weather Service office “work stations” where they alarmed local forecasters. This new feature added a new operational value to the CoCoRaHS network – helping provide early documentation of severe and hazardous weather.

Educational activities grew in importance.  Working with meteorologists from National Weather Service offices in Goodland, KS and Cheyenne, Wyoming, the CoCoRaHS team lead all-day workshops for teachers from rural schools, and conducted more field trips and learning opportunities for volunteers.   

In 2006, CoCoRaHS was the recipient of an important “environmental literacy” grant from NOAA’s Office of Education.  This grant specifically funded expansion of the CoCoRaHS program nationally utilizing and leveraging partnerships with State Climatologists, National Weather Service offices, universities and other interested groups.  Using a thoughtful strategy of first building state-based local leadership teams, CoCoRaHS began a slow, but methodical expansion across the country from 2006 through 2009. (   Newspaper articles, TV news features, e-mail listserves, word of mouth and National Weather Service website announcements helped spread the network to all fifty states and the District of Columbia.  The last state to join was Minnesota in 2009.  Not only were our observers learning about the environment and rainfall patterns, but they were providing the nation with a daily pool of valuable rainfall data.  By 2009, the number of active volunteers grew to over 12,000 making CoCoRaHS the largest source of daily rainfall measurements in the country.

CoCoRaHS - Celebrating 20 Years: The Accidental Network

State by state, CoCoRaHS grew to cover all states and most counties.  Then the winter of 2010-2011 came along leaving a deep and widespread cover of snow and ice across the upper Missouri River Basin and parts of the southern Canadian prairies.  As this snow melted in spring, torrents of flood waters inundated extensive areas of North Dakota, eastern Montana, and the entire flood plain of the Missouri River downstream all the way to St. Louis.  Our Canadian neighbors also suffered weeks of hardship as flood waters from the Prairies made their way to Lake Manitoba and Lake Winnipeg. Lack of adequate data was blamed for some of the difficulties in predicting the magnitude, extent and timing of the flooding. The Canadian Wheat Board along with the Province of Manitoba reached out to CoCoRaHS and within a few months “CoCoRaHS Canada” was born. This Provincial effort quickly grew and now all parts of Canada can participate. This expansion required the addition of metric units and a French-language version of the website and some training materials.  With the help of NOAA, Puerto Rico (2014) and the U.S. Virgin Islands (2015) joined the network next.  More recently in just the past two years, the World Meteorological Organization (WMO) in collaboration with NOAA, helped sponsor a CoCoRaHS pilot project in the Bahamas.   Both Canada and the Islands of the Bahamas have taken well to CoCoRaHS and trust and use the data extensively.

It is the quality and reliability of the volunteer-collected precipitation data from CoCoRaHS that has been our best asset.  Thanks to all our thousands of dedicated volunteers for helping achieve this reputation.  Also, our consistency in how we measure, the gauges we use, the training we provide, and the documentation of station locations and changes (referred to as “metadata”) all meet high standards. When we started back in 1998 we hoped for useful data but didn’t expect it to match or even exceed the requirements and expectations of existing official Federal networks.  

Yet, independent testimonies from many data users such as the National Weather Service, the U.S. Department of Agriculture, research scientists, businesses, State Climatologists, and others consistently found that CoCoRaHS data – rain, hail and snow – were all “research quality – and at least comparable to precipitation data from official sources”.  

Already more than 10 years ago, requests to export CoCoRaHS data to merge with official data collection networks began ramping up.  First it was MADIS – the NOAAs Meteorological Assimilation Data Ingest System -- that began to routinely export and use our data. Then in 2010 NOAA’s National Center for Environmental Information notified us here at CoCoRaHS headquarters that, on the merit of our data quality and extent, they intended to begin incorporating all daily reports from any volunteer who had submitted at least 100 reports in the Global Historic Climate Network – the primary data set used by scientists, businesses, educators and the public for monitoring local, regional, national and international climate conditions.  This meant that CoCoRaHS data ae archived and shared, right alongside National Weather Service Cooperative and Airport network data and similar networks from other countries around the world.  This put some pressure on us – especially considering we encourage participant by volunteers of all ages and typically add a few thousand new “rookies” each year. So some are inevitable, and practice makes perfect.  In response, we maintain a “Help Desk” to promptly answer phone or email questions from our volunteers. We also keep a meteorology student intern and/or professional meteorologist on staff as our “Data Quality Control Specialists” to make sure that potential errors are identified and rectified promptly.

To wrap up, we never planned to become a national network and certainly not international too – but it happened.   It is amazing what a bunch of motivated volunteers can do when given the tools and presented with a challenge.  We just wanted to learn more about the variation of precipitation on small local scales – but we’re learning so much more.  

CoCoRaHS - Celebrating 20 Years: The recent years

As CoCoRaHS became a national network, the decade of the teens saw CoCoRaHS mature.  Growth continues but at a slower rate.  We continue to add over 3,000 new volunteers each year, but attrition has also begun to take its toll as nearly that many also drop out or age out.

The defining features of the recent years are greater educational content, more data collection and analysis opportunities, and a higher performance database working behind the scenes.  We began actively recruiting teachers and schools – producing lesson plans and activities that meet state and national standards.  Observers were given the chance to add the measurement of Potential Evapotranspiration to their daily observations, looking at the other side of the water cycle.  A Climate Resources guide was developed for those interested in gardening and horticulture. Oregon State University’s PRISM climate group, became a huge supporter of the network -- providing CoCoRaHS observers from the contiguous 48 states a tool to look at the long-term average precipitation conditions for their location as well as estimates of local precipitation for every month back to 1897.  A series of live webinars called CoCoRaHS WxTalk began and gave observers the chance to hear presentations on a variety of important topics from clouds to snowfall to waterspouts and even tsunamis, presented by top experts in their fields. Over sixty of these have been recorded and are currently available for the public to view.

In collaboration with the National Drought Mitigation Center (NDMC), the National Integrated Drought Information System (NIDIS) and the Carolinas Integrated Sciences and Assessments (CISA) team, Condition Monitoring was introduced and continues to give observers the chance to report what their landscape's condition (wet, normal, dry) is during any given week.  Recently a mapping system was deployed to show these reports in context with the U.S. Drought Monitor weekly map.  Information has proven invaluable to those who look at drought across the country.  This type of information is now being extended to Canada as well.

CoCoRaHS March Madness, our friendly observer recruiting contest between the fifty states, became ever-more popular as the decade went on. CoCoRaHS educational animations were developed during these years and have brought a whole totally new dimension to online learning.  Other opportunities and content include Field Photo Weekends, state newsletters, a series on state climate descriptions, soil moisture and many, many more. 

During these past eight years we offered observers something to hang on their walls (rain gauge calendars) and something to wear on their backs (a series of precipitation shirts) and head (CoCoRaHS caps).  Our upcoming 7-day June fundraiser will offer donors CoCoRaHS Nalgene water bottles.  The CoCoRaHS mobile device App, introduced in 2014, provided a fast, convenient and easy way for observers to report their daily measurements. While it’s been hard to maintain some of the friendly and personal relationships that characterized CoCoRaHS in its early years, social media (blogposts, Twitter and Facebook) have succeeded in maintaining some of the relational aspects some of us really crave.  Meanwhile, as so much has changed and been added, the basic look and feel of CoCoRaHS has remained largely unchanged over these yeas – and that’s good!    

CoCoRaHS - Celebrating 20 Years: Extreme Precipitation Events


As mentioned earlier in this series, CoCoRaHS was born from a remarkable rainstorm and flood: the Fort Collins flash flood of July 1997.  Over the distance of just a few miles, there were differences of over 12 inches of rain, with the east side of Fort Collins receiving a modest summer rain while the west side was being deluged.  Nolan Doesken recognized that there was very little information about these huge differences in rainfall, and founded CoCoRaHS to fill that need for high-quality, high-density rainfall measurements.
And in its 20-year history, CoCoRaHS has greatly contributed to the understanding of how rain falls in extreme events.  As you might guess, many of these big storms occur in rainy places like Texas and Florida (more on those shortly), but even observers in northern states have collected some huge amounts in their gauges.  Hurricane Ike brought moisture all the way to northern Indiana in September 2008, causing a gauge overflow (more than 11"), and a major storm over Long Island, New York in August 2014 dropped over 10 inches of rain in two observers' gauges.
But there have been some recent major events that are perhaps more memorable.  The August 2016 Louisiana floods and the devastation caused by Hurricane Harvey in 2017 were thoroughly documented by CoCoRaHS observers, and have contributed invaluable information to forecasters and researchers studying these remarkable storms.  And just recently in April 2018, the all-time record 24-hour total measured by a CoCoRaHS observer was set: 36.49" on the island of Kauai, Hawaii.  We can't thank our volunteer observers enough for their dedication to measure the rain, even when they have to dump out their gauges multiple times with danger and damage in their neighborhoods.
And we can't neglect to mention the major flood in CoCoRaHS Headquarter's backyard (northern Colorado) in September 2013.  The value of the network was demonstrated again during this event, as the detailed maps of rainfall that were generated showed what is possible as Nolan's original vision for citizen precipitation observing in Colorado has been fulfilled.
To learn more about some of the extreme rain amounts observed by CoCoRaHS, see this blog from MetStat.


CoCoRaHS - Celebrating 20 Years: 
What has CoCoRaHS taught us ... a 20-year perspective

Our experiences are certainly not all the same.  Nolan Doesken, CoCoRaHS’s founder shares his below.  He’s learned more than he ever imagined and continues to learn – both as a rain gauge participant and as a project network leader.  He says he could elaborate on each item – but that will wait for another day.  Here is just a partial list of his observations.

About precipitation and measurements:

It is really fun to track the statistics of precipitation -- Many never tire of it. 

Precipitation varies a lot – even more than you would think.  Even across the flatlands of Central Illinois daily precipitation across any county usual varies by at least a factor of two among stations, and often more than a factor of 10 (i.e.  from less than 0.10” to more than 1.00”).

CoCoRaHS rain gauges are good, but not perfect.  There is no perfect rain gauge at any cost.

Automated rain gauges are convenient and very informative.   But the most reliable and consistent source for accurate precipitation totals is still an interested volunteer, using a good-quality manual rain gauge, measuring and reporting diligently.

Snow takes a lot more time and determination to measure.  About 15% of our volunteers take the winter off.

Wind driven snow is impossible to measure.  But with training, practice and common sense, very useful estimations can be made

About precipitation data:

Data are fun to look at.  Tables of data are useful, but charts, graphs and maps bring the data alive. Without our CoCoRaHS mapping systems, there would be no CoCoRaHS.

About geography and precipitation:

North America is huge. Even on the driest of days, it is always raining or snowing somewhere.

Mountains and coastlines have a large impact on storms and precipitation patterns, but lakes, large river valleys and other more subtle topographic features also make a difference.   One example that we had no idea about was that the east coast of Florida could sometimes get huge mid-winter rains from seemingly minor disturbances.  How does that happen?  We’re still learning.

You can roughly approximate the fraction of the area receiving precipitation by counting the fraction of weather stations reporting precipitation.  It typically ranges from less than 10% on very dry days to more than 50% on very wet days.

About our rain gauge volunteers:

The power and potential of motivated volunteers is boundless.  We are most convinced of this when we check the CoCoRaHS website on a cold and dark winter morning and still find more than 10,000 dots on the CoCoRaHS maps. Now that’s dedication!

Only about two-thirds of all volunteers that sign up for CoCoRaHS ever actually get started.  Of those that take their first measurement, only about 66% stick with it for more than a year.   But those that measure through the first year are likely to stick with it for several years.

On any given day there are at least 5,000 CoCoRaHS rain gauge volunteers equipped with a working rain gauge, but unfortunately don’t report their measurements.  In this busy world, sometimes we forget.

To maintain the current size and distribution of the CoCoRaHS network in North America, we need to recruit at least 4,000 new volunteer each year.  You can help by telling a friend or relative.

There is no one ideal way to recruit rain gauge volunteers (although National Weather Service Skywarn training is a great place to start, as well as the National Weather Service page headline and local newspaper articles).  What works well in one part of the country may not work at all in others.

Some CoCoRaHS observers love writing detailed comments on their daily reports, but often they are the exception.  On average only about 15% of our volunteers enter comments each day – even on days with huge storms and heavy precipitation.  We can only assume that most people aren’t fond of typing. We wish everyone would consider entering a short comment when precipitation has been observed in their gauge, it’s extremely helpful to those looking at the data.

CoCoRaHS changed the whole trajectory of many of our lives and careers – and in a good way.  We’ve made more friends in more places than many of us thought possible.   For Nolan, the challenges, frustrations and animal antics on his little farm became a surprisingly important part of CoCoRaHS communications. 

What have you learned from participating in CoCoRaHS?  We’d like to know. Please share your stories with us by writing to

CoCoRaHS - Celebrating 20 Years: The next twenty years!

Much of what CoCoRaHS is today is a result of good timing, great partners, and motivated volunteers — Lots of them! Can this continue? Indeed it can!  But there will be challenges along the way, And changes to technology that we probably can’t even come close to predicting. 

There is a lot about the future that we don’t know and don’t need to speculate about.  But we can be assured that whatever the future brings us, rain, hail and snow will still be important, probably even more so than they are today.  High quality precipitation data will still be in demand. 

Here are some questions to consider as we move forward. 

1) Will we be able to reach 20,000 precipitation reports per day?

It certainly should be possible as we already have over 20,000 volunteers equipped with rain gauges and prepared to report. So far the most reports on any individual day is only about 13,500 and the growth rate has been very slow over the last three years. So 20,000, while possible, will take a concerted team effort?

2)  Will CoCoRaHS transition to accept data from automated rain gauges? 

A few other organizations have systems in place to do this, and we’re not inclined to replicate that. Furthermore, the most reliable precipitation data available continues to be that which comes from motivated volunteers equipped with high quality manual rain gauges. That is an important data niche that we will continue to fill. 

3)  Will we expand to more countries? 

As opportunities arise, the chances are good. Currently, we are not equipped or funded to do so in an efficient manner. 

4) Will we keep the “community” in CoCoRaHS?

We sure hope so. With so many people distributed over such a large region, and with everybody being so busy, it’s a challenge even with electronic communications to stay in touch like a close family. But we will keep trying and we welcome your suggestions. 

5) As we get older, will we need to find some younger observers as replacements? 

Looking in the mirror, that answer becomes pretty obvious. Current demographic trends are not favorable.   Many younger people are congregating in densely populated urban areas. But, as those people get older and some have families, chances are that quite a few will relocate back to rural and suburban areas again and will form the basis of the future core CoCoRaHS volunteers. We are optimistic!

As we complete our celebration of our 20th anniversary of CoCoRaHS, we just want to say what a joy it has been working with all of you. We look forward to many more years together.