Ag Weather Forum

IRI Forecast Raises Summer Midwest Precipitation

Bryce Anderson
By  Bryce Anderson , Ag Meteorologist Emeritus
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The IRI updated seasonal forecasts have normal to above-normal rainfall for the June-through-August stretch in much of the Midwest. (International Research Institute for Climate and Society graphic)

May 14 brings an indication that one closely watched public weather forecast source is suggesting a more favorable rainfall pattern for much of the U.S. Corn Belt during the upcoming 2021 summer season. The reference is to the May forecast update from the International Research Institute for Climate and Society (IRI). The IRI's seasonal forecast released in mid-May shows the suggestion of near- to above-normal precipitation over almost the entire Midwest. This includes most of Iowa, which experienced notable losses a year ago when a mid- to late-summer La Nina Pacific Ocean temperature pattern combined with a devastating derecho windstorm to drag down yields.

The IRI forecast notes a move to neither El Nino or La Nina in the Pacific Ocean forecast for the 2021 summer season of June through August. "SST (sea surface temperature) forecast indicates that the La Nina event has transitioned to ENSO-neutral and will likely remain so through the boreal (northern hemisphere) summer," stated the Institute in its forecast announcement release.

Moisture prospects for the Midwest are notably wetter in the latest IRI depiction than in recent public and private provider forecasts, including the DTN seasonal forecasts as recently as May 12, which called for below-normal precipitation over the northern and central U.S., including the Midwest. In addition to the revision showing the majority of the Midwest with higher chances for at least average precipitation, central Saskatchewan in the Canadian Prairies is also tagged for enhanced precipitation in the IRI forecast.

On the other side of the precipitation spectrum, the IRI forecast has below-normal amounts for the summer over northern Minnesota along with most of the Plains, central and western Texas, and the western U.S. Only a swath of the Intermountain West has a chance for above normal precipitation.

It will be interesting to see how forecast updates from other sources, scheduled for release during the upcoming week of Monday, May 17-Friday May 24, display the central North America precipitation outlook. For example, frequently the NOAA Climate Prediction Center (CPC) forecast closely tracks the IRI depiction. If that occurs again, there could be more attention given to the prospect for useful summertime precipitation; and in addition, higher chances for trendline or above trendline corn and soybean yields.

Bryce Anderson can be reached at

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