July 19, 2013

Iowa bounced back from one of its worst droughts on record with this year's soggy spring, but now the weather has shifted again, and the state stands on the precipice of another potential disaster.

Under the withering rays of an Iowa sun, some fear what has become known as a "flash drought."

It's not a technical term - in fact, Iowa is still a long way from an official drought, weather officials say - but it's not the first time the state has seen weather change dramatically and rapidly from bad to worse.

Harry Hillaker, state climatologist, said there are at least two other times in recent history when the Midwest experienced such a sudden change. In 1983 an unseasonably cool, wet spring preceded one of the hottest and driest summers on record, with multiple weeks of three-digit temperatures.

The summer of 1947 was another example of the flash drought - bigger and worse than any other on record.

"This year the transition, you might say, may have been a little slower," Hillaker said.

Carroll's rainfall this year was about 4 inches more than normal through the end of June, mostly due to a soggy May that accounted for 3 of those excess inches.

But Carroll has lacked significant rainfall for more than three weeks. Total precipitation for this month sits at a meager .07 inch - about 5 inches is normal for the entire month.

About one-fifth of the state is abnormally dry, according to the U.S. Drought Monitor.

What has spared residents and fields from drought is that temperatures haven't been too extreme.

The heat "is kind of to be expected in late summer. It hasn't really been excessively hot." Hillaker said. "You can get by without much rain as long as temperatures aren't excessive like they were last year."

Still, the weather will need to change if a drought is to be avoided.

"Lower temperatures would help," Hillaker said. "Higher humidity would actually help as well, even without the rainfall."

He said the likely reason for this dry spell is that the soil was so dry following last year that it took every inch of the spring deluge just to replenish the groundwater supply.

Hillaker said another problem is, in addition to the heat, there has been relatively low humidity, with a dew point average of around 60 degrees.

"Things dry out really quickly at that point," Hillaker said.

A two- to three-week cushion before a drought could really settle in gives farmers some hope, Hillaker said. However, agriculture may feel the effects before a drought hits. In fact, Mark Licht, Iowa State University Extension and Outreach field agronomist, said crops are already beginning to feel the heat.

"We're probably already to that point," Licht said. "Already seeing some heat stress."

Crops are fighting higher odds this summer as they enter their pollination periods because of planting delays.

After a late planting season due to rain, many of the crops - corn in particular - have not grown full root systems as they normally would have by now. Without fully developed roots they cannot reach the water that can only be found farther and farther down as the soil dries out.

Licht said the biggest danger will come around pollination time.

"Right after pollination, plants will be taking up the most moisture it will use all season," Licht said.

During this time the kernels are absorbing as much moisture as they can, but without a steady water supply corn will not fill out, limiting yields.

National Weather Service forecasts show a 50-percent chance of rain over the weekend, though crops will need more than that to stay healthy.

"We're at a bit of a disadvantage," Hillaker said. "Even though we had a lot of moisture, if we were to stay dry - equally dry as the last few weeks - we could see a similar impact on crop yields as last year."