Drought conditions are likely to develop over the southern half of the state in August as the month starts with a string of abnormally hot days with little chance for rain, according to the U.S. Drought Monitor.
The portion of the state that is abnormally dry or in varying degrees of drought expanded last week to more than half of the state. It’s the first time the dry area has been that large since April, when persistent rains delayed corn planting. The latest Drought Monitor report on Thursday showed an expansion of severe and extreme drought in northwest Iowa and the extension of abnormally dry conditions across much of southern Iowa.
“In all honesty, we are kind of at a pivotal point this week, depending on what our temperatures do,” said Aaron Saeugling, an Iowa State University Extension field agronomist who monitors southwest Iowa. “Our water demand just grows exponentially.”
He said farmers’ worries about their crops have worsened as available soil moisture has quickly deteriorated in the past two months. The area’s total rainfall ranged from a half to 1.5 inches of rain for the entire month of July, he said, compared with the normally expected amounts of more than 4 inches.
Southwest Iowa previously led the state in available soil moisture, according to U.S. Department of Agriculture reports. In early June, about 96% of its topsoil and subsoil had adequate or surplus moisture. As of Sunday, about 27% of topsoil and 36% of subsoil had adequate water for crops to grow.
The stress on the corn is most apparent in the afternoons, Saeugling said, when the plants roll their leaves to retain moisture.
“They are basically shutting down photosynthetically,” he said. “And they’re in the reproductive phase, so that affects grain yield.”
The National Weather Service issued a heat advisory for Tuesday afternoon for roughly the western half of the state. Actual temperatures are expected to approach or exceed 100 degrees, and high humidity will make it feel much warmer. The heat index for Council Bluffs, for example, was predicted to be 108 degrees.
“We’re in a pattern that essentially is causing warm air to get pulled in from the south,” said Dylan Dodson, a meteorologist for the National Weather Service. “It’ll cool off a little bit — relatively speaking — but it will stay hot through the end of the weekend. … The 8-to-14-day outlook keeps us hot.”
The “relative” cooling happens after Tuesday, when there is a chance of scattered storms across the state and a reduction in high temperatures on Wednesday of 5 to 10 degrees. But that still means much of the state will reach the high 80s or 90s.
Justin Glisan, state climatologist for the Iowa Department of Agriculture and Land Stewardship, said he expects the dry conditions to expand in the early part of August but said the month has been trending wetter in the past decade.
“The law of averages, that’s how I’d like to see things,” he said. “We have the hot snap and then maybe see below-average temperatures and more rainfall.”
Last week, the state averaged temperatures of about 3 degrees cooler than normal with abysmal rainfall, Glisan wrote in his weekly report for the USDA. Much of the south had no rain, and the highest reported rainfall accumulation was .89 inch near Churdan.
Crop conditions suffered: The state’s corn was rated 76% good or excellent, down from 80% the previous week. Soybeans were rated 73% good or excellent, down from 75%.
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