1. IEM Homepage
  2. IEM Ag Weather/Climate Information

The IEM website contains data from many different observation networks. While you may know what you are looking for, figuring out which network has this data is tricky. This table is an attempt to help you locate the data / product you need. Please do contact us with your questions!

IEM's most popular applications: Automated Data Plotting Climodat IEM Explorer Single Site Graphs USDA NASS Products

Variable Timescale / Reporting Interval
Seconds/Minutes Hourly Daily Weekly/Monthly Seasonal Yearly
Air Temperature ISU Soil Moisture stations record real-time data at one minute intervals. ASOS also provides data at such frequency, but it is delayed by ~24 hours. ASOS/AWOS are stations located at airports and are the baseline weather observation network. The ISU Soil Moisture network has data for Iowa. NWS COOP has high quality high and low temperature reports for 24 hour periods, not always for the calendar day. The Climodat reports contain summarized data from the NWS COOP network.
Plot of Daily Departures by Year

Pest Maps and Forecasts track degree days for various pests of interest.
Growing Degree Days Not applicable The NWS COOP network data contains the best quality information for daily temperatures, but they are not always on a calendar date. The Climodat reports present summarized GDD data.

Maps of Growing Degree Days:

Pest Maps and Forecasts track degree days for various pests of interest.
Precipitation (liquid + melted snow) The IEM processes the one minute Iowa ASOS data, but there is a month delay for receipt of this data. The ASOS (not AWOS) sites include a heated sensor that melts snowfall to produce liquid equivalent. The NWS COOP network report precipitation totals that include melted snowfall.
The IEM processes gridded analyses of precipitation
There are daily ASOS precip reports available for download.
Rainfall (liquid only) The SchoolNet sensors do report minute rainfall, but the data is not of great quality. The ASOS/AWOS sites report hourly rainfall as well as the ISU Soil Moisture network.
Solar Radiation The ISU Soil Moisture network collects solar radiation at minute and hourly intervals. The ISU Soil Moisture network makes daily summaries available. The IEM also provides estimated radiation data for download for NWS COOP sites based on model analyses. The model analyses (MERRAv2, HRRR, NARR, and ERA5Land) used to provide solar radiation data for the NWS COOP sites and be summarized over time here:
  • Autoplot 107 has daily averages over a period of your choice.
Soil Moisture The ISU Soil Moisture network collects five minute and hourly soil moisture data. The Iowa Daily Erosion Project produces soil moisture analyses based on a model called WEPP. Summarized data for this timescale does not exist on the IEM at this time.
Soil Temperature The ISU Soil Moisture network collects five minute and hourly soil temperature data. The ISU Soil Moisture network produces daily summaries of high and low temperature. Summarized data for this timescale does not exist on the IEM at this time.
Snowfall Does not exist The NWS has paid snowfall observers that report 6 hour snowfall totals, but the IEM does not have a good interface to get this data. The IEM collects the 24 hour snowfall reports from the NWS COOP network. Summarized data for this timescale does not exist on the IEM at this time.
Stress Degree Days Not applicable The NWS COOP network data contains the best quality information for daily temperatures, but they are not always on a calendar date. The Climodat reports present summarized SDD data.
Wind ISU Soil Moisture stations record real-time data at one minute intervals. ASOS also provides data at such frequency, but it is delayed by ~24 hours. ASOS data is typically the best at this temporal scale.

Windroses are neat visualizations of wind direction and speed frequency. The link takes you to the interface for the Ames Airport. You can switch stations to find the same for other locations.

USDA NASS Products

The IEM attempts to sync much of the USDA NASS data into our database. A number of automated plots are available for this data (search for NASS in the dropdown menu).

The IEM also attempts to glean the Iowa Ag Reporting District data found in the weekly weekly crop progress PDF reports. You can download the IEM's entire database as this Excel file.

Historical Freeze Risk

An air temperature less than 27 is generally considered to be the Hard Freeze, that is a crop killing event, although plant damage and yield loss is often observed at less extreme low temperatures. Crop threshold temperatures for plant damage in Fall differ from Spring thresholds (mainly because of plant size/height).

External Links