Frequently Asked Questions


How do I join the network as a volunteer observer? Click on the "Join Us" section and fill out the registration form.  You will be assigned a station number and will be contacted by our station administrator with some welcome information.

Are there other things I can do to help the network? Yes, volunteers are a most treasured resouce and we have many ways that you can help. Please check out our Help Us page for more details.

What process happens when I sign up to be an observer? After you submit the application, a Station Number will automatically be assigned.  You will receive an automatically generated email with your Station Number and Login information.  The Station Administrator will then calculate the longitude and latitude for your station if you have not provided that information.  Your station will be assigned a Station Name . You will then receive our Welcome Email that includes your Station Information and Coordinator information along with training information. You should attend a CoCoRaHS training before entering data into our system (You may either train on line or sit in on a local volunteer training if one is available in your area).

Why do you need longitude and latitude?
We use that information to map your data. Please let us know if your data appears to be mapped in the wrong location.

Why do I need to attend a training session? We are trying to get the most consistent data possible using volunteer observers. We hope that you will be able to attend a training session, or at least read all of the on-line training information before entering data. We care about the accuracy of our data and hope that you will too.

When can I begin entering data? You may begin entering data as soon as you have been assigned a station name and station number and have attended a training session. Your data will appear on the Web immediately in both report and map form.

What does the station number mean?
The station number is generally the abbreviation of the state that you live in, followed by your county followed by two or three number. Example: CO-LR-284. This would be Colorado-Larimer County-Station 284.

What does the station name mean?
The station name is generally the town name followed by a distance in decimal miles and a direction. For Example: 'Fort Collins 4.5 SW' means that you are approximately 4.5 miles Southwest of the geographical center of Fort Collins. The names are based on the direction and distance from an arbitrary point in a town or city based on coordinates provided by the National Weather Service.

Who is my Local Coordinator?
You may find your local coodinator by clicking on the following link:  If you don't see one for your county, please contact your state coordinator.

Do I have to check my rain gauge at 7am? No, but we would prefer it if you did. If you check your gauge at other times, your data may not be directly comparable to other data. If you check your gauge at night, your data will be in our reports but won't show up on our maps. We only map data that is collected within two hours of 7am.

Who will answer any questions I have about the CoCoRaHS network?  You should first try contacting the Local or State Coordinator for your area. You may also contact CoCoRaHS Headquarters during normal business hours at: (970) 491-8545 or (970) 491-1196.  Learn more at our Contact Us page.

Who do I e-mail with any questions or comments about the web site?  Any questions regarding the Web site should be directed to our general e-mail , which will be forwarded to our Web masters.

Where is CoCoRaHS Headquarters located?
   We are located on the Foothills Campus of Colorado State University in Fort Collins, Colorado. Please stop by the next time you are in the Fort Collins area.

Why does CoCoRaHS not use automated rain gauges? (click here to open or download a PDF of this answer)

We are often asked why CoCoRaHS does not accept data from automated rain gauges to report daily 24-hour precipitation totals.  After all, many weather enthusiasts already have electronic home weather stations with automated rain gauges that record precipitation.  Do they really need to acquire a manual CoCoRaHS gauge?

Unfortunately, rain gauges are not all created equal and do not all report the same.  The Colorado Climate Center has been involved in rain gauge studies for many years and have had dozens of volunteers like you test their automated gauges against either the CoCoRaHS 4" diameter manual gauge or the National Weather Service (NWS) 8" diameter manual Standard Rain Gauge.  We have also tested National Weather Service Automated Surface Observing System automated tipping bucket rain gauges (not unlike the tipping bucket gauges that come with many home weather stations, but larger, sturdier and a lot more expensive).

The NWS and CoCoRaHS manual gauges compare very well with each other over wide ranges of weather conditions. Tests conducted in Colorado over three decades indicate that the CoCoRaHS gauge has a collection efficiency of 101-105% compared to the standard NWS gauge in side by side measurements.  Nearly all daily differences were small – usually 0.02” or less with much of the difference attributed to greater wetting required by NWS gauges before registering the first 0.01”.
Because of the performance and accuracy of the 4” diameter high capacity manual precipitation gauge, the National Weather Service and its parent agency, NOAA, accept data from CoCoRaHS as comparable to their official instrumentation. By comparison, the majority of automated rain gauges report less precipitation than the reference NWS Standard manual rain gauge, especially when summed over several months or years.    Daily differences are larger – sometimes 10% or more – especially for storms with high intensity rainfall. Moreover, none of the automated gauges work well in areas that receive snow.  This is not acceptable for our project because we are interested in observing and understanding natural precipitation variability, as accurately as possible, under all precipitation types and intensities.  If we permit the use different kinds of gauges with different abilities to catch and report precipitation, it becomes difficult to determine if differences in rain or snowfall are "real" or due to the kind of instrument that was used to report the measurement.

Therefore, we require all of our observers to set up a CoCoRaHS 4" diameter manual gauge and use that for your daily reports.
We do recognize the value of automation and certainly don’t discourage the use of electronic instrumentation.  They are great for showing the timing and relative intensity of precipitation along with other weather conditions, whether or not you are home to experience it.   They can be used in combination with the CoCoRaHS manual gauge to show when precipitation began and ended and was most intense.  It can provide useful redundancy as well as a backup when an observer is away.  If you do use an automated gauge for a measurement on a particular day, we request that they mention that in the "observation notes” for that day.
For those of you who already own a good quality automated weather station and decide it's too much trouble to purchase a CoCoRaHS gauge and take manual measurements  you may still be able to share your data with the National Oceanic and Atmospheric Administration (NOAA - the organization that oversees the NWS) via their Citizen Weather Observation Program (CWOP).  This program makes home weather station data available to the NWS for certain real time applications. WeatherUnderground is another system for web-based data sharing.  

For climate data and research applications, as well as supporting the "NowCasting" goals of NOAA, we encourage you to obtain the 4" diameter high capacity manual rain gauge and join CoCoRaHS. 

How can I measure precipitation if I am visually impaired?

The primary method involves a talking measuring cup. Click here to read detailed instructions.