Ag Weather Forum

Summer Heat, More Active Weather Coming to Corn Belt

John Baranick
By  John Baranick , DTN Meteorologist
The DTN high temperature forecast for June 16 will be a common sight for next week. (DTN graphic)

It has been a hard spring for many farmers this year. Wet weather has made planting and other fieldwork difficult -- and in some places impossible. Soils around most of the Corn Belt have become very wet, but otherwise well-stocked as the early growth period takes over for newly planted corn and soybean seeds. Crop condition ratings continue to be very high for this time of year, which is putting the 2024 campaign off to a good start. Though some areas would like to see a little rain continuing and others would like to see it hold back, overall the crop is in a good position to start the season.

A major weather change is coming that could make those looking for some rain hurt a little more. An upper-level ridge of high pressure, which is currently over the western U.S., will shift to the east by this weekend (June 15). That will result in several changes to the weather patterns across the U.S. but specifically in the Corn Belt.

First, the ridge will promote an increase in temperatures. Thus far this season, temperatures have been mild to warm, but rarely hot and only for a day or two between storm systems. Those in Texas may beg to differ, but for the majority of the country east of the Rockies, that has been the case. Of course, it has been "summer" for all of 11 days, but it looks like summer heat will be returning. We will see a dose of it this week, but will really turn up the thermostat this weekend. Those east of the Mississippi River will see the greatest anomalies above normal, but many areas east of the Rockies are going to see temperatures reach up into the 90s. That could start to stress young seedlings that have limited root zones that do not see any rain.

The second effect will be to increase humidity. With the ridge moving into the East, the clockwise flow around it will move air from the Gulf of Mexico northward through the middle of the country. The increase in both heat and moisture will be uncomfortable for livestock and anyone working outside, but also for plants. The moisture may have the effect of decreasing high temperatures either through cloud cover or increased showers, the latter of which is very questionable by models.

And the third feature will be an active storm track on the ridge's western edge. Not only will the ridge shift over into the East, but a trough will take its place in the West. The trough will supply energy into the middle of the U.S. while the ridge supplies the heat and humidity to create widespread areas of showers and thunderstorms and potential for severe weather.

The current forecast is for a priming storm to move through the Canadian Prairies on June 14 and push a cold front into the Northern Plains and Upper Midwest. That front is forecast to stall out in this general area through most, if not all, of next week. Disturbances from the western trough will ride along it and produce areas of rain and thunderstorms from Nebraska to Wisconsin and points north throughout the week. Temperatures near and north of the front will be markedly cooler than the 90s forecast south of it.

Adding up the model forecasts through June 20, the European ECMWF model has widespread areas of 1 to 3 inches of rain through this region and some areas exceed that. This would be unfortunate for some areas of the eastern Dakotas and Minnesota that have been awfully wet recently and have ponding and significant wet spots in their fields. But for others, especially those in much of Nebraska and Iowa, will welcome the rain to continue overall good crop ratings.

There will be real concern for those farther south and especially east. The Eastern Corn Belt has only had limited rainfall over the past week. Areas like Illinois and Indiana have had streaky, mostly light precipitation over the last week that are leaving some areas on the drier side already. With the focus of rainfall generally west of these states, those here and even farther east will go through some summer heat without a lot of relief. Shallow root systems could see corn and soybean plants having some early stress. Those in the Southeast U.S. that are away from the immediate coast will find harsh conditions as well.

Models do not necessarily agree on the precipitation forecast, though. The American GFS model is much more generous to the Southern and Eastern Corn Belt than the ECMWF is. This is largely due to the influx of tropical moisture from the Gulf of Mexico. The GFS spreads this through more of the Corn Belt. But even though it produces more rainfall than the ECMWF, it is still spotty and lacking in most areas.

Even if the GFS is more correct than the ECMWF, we could still see some areas of flash drought developing in the heat in areas that had been saturated just a couple of weeks prior.

The real question will be "how long does this last?" and there is no perfect answer for it. Models indicate the eastern ridge will be in place through at least June 24, but that ridge may shift westward for the last week of June. If it does, the Western Corn Belt would see temperatures remain hot while eastern areas get a limited break. But then we could be looking at an increase in severe weather depending on the extent of that ridge. Those details will need to be worked out.


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