DES MOINES, Iowa, January 8 – Factor the wind chill in, and the northeast Iowa town of Olewein was struck with temperatures at a sobering -51° Fahrenheit on Monday, and across the state the ground is frozen roughly a foot deep.
But historically, how cold is it, really?
State Climatologist Harry Hillaker says there are a few metrics to use. He says the first is actual temperatures.
At the time of his interview Monday, Hillaker said the lowest reading he’d heard of was from Cresco in northeastern Iowa, at -23°F. But earlier in January, a -24°F reading was taken in Elkader in northeast Iowa, and on Christmas Eve, temperatures fell to -27°F in Osceola in southern Iowa.
The second metric is measuring the wind chill.
“For that one,” Hillaker says, “you have to go back to 2010, about four years ago, the last time we had a lower wind chill, and that wasn’t much lower. I think it was minus 53, at that time. So minus 50 wind chills don’t come along nearly so frequently, maybe once every five years or so, on average. So that aspect of it, you know, is a bit more unusual.”
Hillaker says the duration of the cold is the third way to measure it. In those terms, he estimates the cold spell spans Saturday to Wednesday, and a stretch like that, he says, only happens every 5 to 7 years.
In agricultural terms, Hillaker says temperatures this low can be both good and bad, depending on which crop you’re growing.
“As far as soil goes,” Hillaker says, “It’s somewhat helpful to have a decent amount of soil frost, to help freeze it, thaw it, as many cycles as you can go through would help reduce compaction, and things like that, that might be generated during a wet spring, like we had last year, to help stir things up a bit.
“It could cause trouble, though for things like alfalfa – perennial sort of vegetation – where it might result in winterkill: having things too cold, too long.”