Iowa Environmental Mesonet

Iowa State University Department of Agronomy

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IEM Rainfall

IEM rainfall is a high resolution depiction of rainfall estimates over the state of Iowa. These estimates are provided freely via the Internet with no warranty or claim of accuracy. Currently, there are a number of ways you can view/download this dataset.

Request Data by Point

Instructions: With this form you can request daily estimates of rainfall for a particular year and for a particular point. This point can be specified in a number of ways. Caveat: Geocoding is not perfect. Your address may not be found in the database. If you first attempt fails, try using a popular building address for a location near you.

Select Year:
View Options:

Choose a method to select data point:
Specify Latitude & Longitude Geocode An Address Specify IEM Site ID
Latitude: Street Address: Enter ID:
Longitude: City in Iowa:

Daily GIS Shapefiles

Instructions: Please select the date you would like to download a zip file containing a shapefile of rainfall estimates.
Month:Day:Year:Coverage Type: Projection:

The point coverage is simply the centroid of the polygon coverage.

OGC Web Services

If your GIS system supports accessing Web Map Service (WMS) or Web Feature Service (WFS) servers, you can directly pull in some of these rainfall estimates from the IEM server. Our WMS URI is: 
http://mesonet.agron.iastate.edu/wms/rainfall.php?
and our WFS URI is: 
http://mesonet.agron.iastate.edu/wfs/rainfall.php?

Pulling data into GIS applications via these services has not been widely tested. If you run into any problems, please let us know!

About Rainfall Estimates

These rainfall estimates are directly based on the Stage 4 precipitation analysis produced by the National Center for Environmental Prediction. The IEM processes this data source in the following ways:
  • Extract data valid for Iowa from the national analyses.
  • Convert the data from Grib format to a relational database.
  • Produce summary totals for the local day instead of GMT day.
  • Provide instant access to this data from this page and others.

Rainfall estimates are produced each day at 3:30 AM for the previous day. These estimates are later revised as more information is made available to better refine the estimates. If you downloaded data for yesterday at the time, you may wish to redownload that dataset again later, since the estimates may be refined then. Sounds confusing. Please contact us if you have questions.