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Corn to be stressed in high temps, low rainfall through next week

Mohler says temperatures starting today (Thursday) will generally be in the upper 80s, mid-90s, and in some places, reaching triple digits.

Very hot, sticky, and certainly uncomfortable is how forecasters are describing the next 10 days across the Corn Belt, making the soon-to-be pollinating corn crop noticeably stressed.

“Corn pollinates better when you’re getting normal rains and normal temperatures,” says Dale Mohler, senior Accuweather agricultural meteorologist. “These next couple weeks of above-normal temperatures and minimal widespread rainfall is going to stress corn in its current critical stage of pollinating.”

Mohler says temperatures starting today (Thursday) will generally be in the upper 80s  to mid-90s, and in some places they’ll reach triple digits. There will be some significant drying, and drought stress will show up in corn. The leaves will be rolling over the next week and a half and corn has a hard time pollinating when it’s dry and hot.

Places that could see corn the most stressed are in the southwest corner of the Midwest where it’s going to be the hottest. This includes central and southern Iowa, Missouri, Nebraska, and into Kansas. Mohler expects the northwest corner could see the most normal temperatures and rainfall including eastern Dakotas and Minnesota.

“It will be a little hit or miss but they’re going to have more opportunities for rain there,” Mohler says. “However, the southwest corner of the Belt is closer to a ridge of high pressure and that’s going to block a lot of those rain bearing opportunities. It’s also a few hit-or-miss rains in the southwest that could measure ¼ of an inch to an inch over the next two weeks.”

Mohler explains it isn’t so much the extreme temperatures, but the persistence of it for six to 10 days. Some places could have eight to 10 days in a row that are in the lower mid-90s.

“It’s a persistent spell, but not extreme. Extreme would be low 100s. Right now we don’t see that, but things wouldn’t have to change much to see temperatures near 100°F. in one or two areas in the southwest corner. But overall, temperatures will be in the lower mid-90s.”

Mohler also says areas that were planted later aren’t in pollination stage yet. Farmers who were later getting in the fields this year, may benefit from avoiding the heat stress on pollinating corn.

“As we head toward the second half of the month, we’re seeing more consistent rainfall developing and temperatures trending back toward normal.”         

As for the soybean crop, Mohler says the most critical stage for soybean growth is later July and into early August. It’s possible the weather is back closer to normal in that time frame, so they’ll be in “survival mode” over the next couple weeks.

Above-normal overnight temperatures

Having the above-normal daytime temperatures won’t be the only thing causing stress on the corn crop. Overnight temperatures will be consistently above normal as well due to very high dewpoints.

“Across the Midwest, we can expect to have some 80-plus degree dewpoints overnight, meaning some of our evenings may not even get into the 70s but hang around the low 80s,” says Dennis Todey, USDA Midwest Climate Hub director. “So, it’s going to be a tough time for crops, livestock, and people working outside.”

“Unlike in June we had very warm conditions with relatively dry conditions for the Midwest. Dewpoints were down in the 50s, but that’s not the case this time. Areas that have received recent rainfall and soil moisture will be in good shape and will be able to manage the heat.”

Todey also notes corn has been bred to handle these stressful conditions better than it used to, but there is still potential incurring some yield loss in corn through this heat wave.

Climatologically the highest temps on average occur about the second, third week of July throughout much of the Corn Belt.

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