Agronomy Team Debuts New Weather Tool for FACTS

New benchmark weather tool added for every crop reporting district in 12 states

September 10, 2020, 8:42 am | Zach Clemens, Sotirios Archontoulis

AMES, Iowa Iowa State University Extension and Outreach has debuted a new tool on the Forecast and Assessment of Cropping Systems (FACTS) website that displays weather summaries for every crop reporting district in 12 Midwest states.

The weather summaries include data from 1984 through today, updated every month and with information on temperature, precipitation, radiation and other weather indicators — like the number of days with extreme weather rain events, or the number of warm nights.

“This new tool provides an easy way for farmers and scientists to benchmark weather at any crop reporting district by month,” said Sotirios Archontoulis, associate professor of agronomy and principal member of the FACTS team at Iowa State University.

weather map.The new Weather Tool enables the user to select a crop reporting district from the nearly 1,000 counties across the Midwest. Once a district is selected, the user chooses a weather variable of interest and the month with the year, and the tool displays benchmarking graphs with options to download the data.

“This data can be crucial for decision-making on the ground and in the field,” Archontoulis said. “Weather is the main driver of yield and soil water/nitrogen fluctuations from year-to-year across the landscape, and having a benchmarking system that can be referenced will inform those decisions.”

This tool has aggregated weather data at the crop reporting district level for the first time, using 100 grids within a single crop reporting district instead of the typical one or two. The range of weather indicators available as well as the flexibility in performing benchmark graphs saves everyone time and gives greater detail than what has previously been available.

The weather data is a synthetic gridded product from various sources, called “IEM Reanalysis” system, which was engineered by Daryl Herzmann, Iowa Environmental Mesonet. The resolution of the synthetic gridded weather product is 0.125 x 0.125 degree latitude and longitude (about 15 km2 resolution). The temperature data generally comes from the NWS COOP observers. The precipitation data come from RADAR based estimates provided by NOAA MRMS, Oregon State’s PRISM dataset and NWS COOP reports. The radiation data come from NASA POWER.

The accuracy of the monthly gridded weather data is sufficiently well as illustrated in the figure. The gridded product captures 99% of the observed variability in temperature, 95% of the observed variability in radiation and 86% of the observed variability in precipitation in single point tests across 11 locations in the US Corn Belt.  

This tool is the product of a collaborative work between Archontoulis and Schnable Labs (Department of Agronomy) and funded by the Plant Sciences Institute at Iowa State.

  • Sotirios Archontoulis conceptualized the tool, performed weather data QC and determined the weather indicators.
  • Cheng-Ting “Eddy” Yeh, systems analysis in the Plant Sciences Institute at Iowa State, developed the web-interface. Pat Schnable, distinguished professor in the Plant Sciences Institute at Iowa State, provided feedback on the concept and development process.
  • Daryl Herzmann, Iowa Environment Mesonet, compiled the gridded weather data.
  • Isaiah Huber and Makis Danalatos aggregated the weather data to crop reporting district level.
  • Mark Licht, assistant professor in agronomy and cropping systems specialist with ISU Extension and Outreach, provided expert feedback on the web-tool.

For questions email:

Sotirios Archontoulis ( or Eddy Yeh (

Original photo: weather map. Caption: Select a crop reporting district, a weather variable and a timeframe to get your graph.

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