Editor’s note: The following was written by Joel DeJong, Iowa State University Extension field agronomist in northwest Iowa, Dennis Todey, Director of the Midwest Climate Hub, and Justin Glisan, state climatologist, for the Integrated Crop Management blog April 13.
It is the time of year when forecasts become a bigger concern for Iowa crop producers.
Nearly everyone has their favorite choice for getting their weather information. In this article we will be sharing weather sites we use when discussing weather issues with our crop production clients.
Fifty degrees is often quoted as the temperature that is needed to begin germination and growth of corn. The Recent 4 Inch Soil Temperature website (bit.ly/36hN6K2), a part of the ISU Soil Moisture Network, shows maps that are based on National Weather Service North American Mesoscale forecast model analyses and short-term forecasts. The ISU Soil Moisture Network observations are used to bias correct the model output after some quality control checks are made. This network site also allows you to see soil temperatures at 12, 24 and 50 inches at selected Iowa sites.
It seems everyone has their favorite app for following rainfall and storm systems. A publicly available network called “CoCoRaHS,” the Community Collaborative Rain, Hail & Snow Network, has rainfall data searchable by site and date. It can be found at cocorahs.org/.
The National Weather Service also has a “Current 1-day Observed Precipitation Map” at water.weather.gov/precip/. You can even find an NWS page with a National Snow Cover Analysis.
If you work with corn growers over a wide region, it is useful to monitor the rainfall, growing degree day and stress degree day accumulations, plus solar radiation differences in that region and compare them to long-term averages. This is called the “IEM Climodat Station Monitor,” another part of the Iowa Mesonet network. The site bit.ly/3rOtCEv provides an example of 8 NW Iowa weather stations’ information from the 2021 growing season. The chart can be tailored to your own selection of weather stations, plus any range of dates you choose to examine.
A good website for weather forecasts on wind speed and direction is the National Weather Service. Go to www.weather.gov/. Enter your zip code in the upper left hand search box. When the forecast page for your location comes up, scroll down and click on the box titled “Tabular Forecast,” or use the “Hourly Weather Forecast”. Both give hourly wind speed, direction, and temperature forecasts for the next six days (two days to a page).
If you need to find a history of wind speed and direction, the Iowa ASOS stations, found at airports, can help. Find them online at bit.ly/3M0hsja. Select a station from the drop-down list, and when that page comes up, click on the “Observation History” tab for data in five-minute intervals. Then select the date or dates you are interested in. Additional data that will be supplied includes temperature, pressure, humidity, snow depth, and precipitation.
The ISU Soil Moisture Network has several locations around Iowa that monitor temperatures and moisture levels at 12, 24 and 50 inches below the soil surface, under a growing crop.
It can be useful to plot a time series (use bit.ly/3JHkZBG). I’d suggest selecting a site near you, the time range you want to watch, then “make plot.”
Nationally, NASA has a website (go.nasa.gov/3KMdI4S) that estimates volumetric and relative soil moistures for different depths. The NWS Climate Prediction Center also posts their Soil Moisture Percentile Data at bit.ly/3roBAE4.
Find the NOAA Climate Prediction Center outlooks at bit.ly/3vhVfXe. If you watch the status of El Niño/La Niña, that outlook can be found at bit.ly/3M6N32R. Finally, the Midwest Climate Hub, a part of the USDA, offers regional agricultural outlooks and weather analysis. Find those at bit.ly/3rv1GoL.
Weather reports for the state of Iowa, weekly, annually, or historic, can be found at bit.ly/3JKWVh0.
Current conditions for your area may also be found by entering your zip code on the AgUpdate weather page.