The term "polar vortex" was introduced into the nation’s vocabulary as frigid arctic air caused temperatures to plunge well below zero over much of the Midwest and Great Plains.
This week, the phenomenon returns – but with a July twist.
According to AccuWeather meteorologist Carl Erickson, that doesn’t mean the U.S. will see anything severe as freezing temperatures or snowfall. But it will get surprisingly cold, with nighttime temperatures dipping into the 50s in many cities and even into the 40s in some suburban and rural areas.
Friday's Accuweather forecast shows the polar vortex dipping into the Midwest this week, bring unseasonably cool temperatures.
Daily highs are expected to be 10 to 20 degrees cooler across much of the Midwest. The Weather Channel is predicting these daytime highs for the following Midwest cities on Tuesday (7/15), for example:
• Des Moines – 70
• Minneapolis – 70
• St. Louis – 74
• Marquette – 57
• Chicago – 67
• Indianapolis – 69
• Detroit - 69
Chris Anderson, the assistant director of Iowa State University's Climate Science Program, says the cooler weather will be a net positive for farmland.
"Cool conditions through pollination means all of the kernels will pollinate," he says. "The No. 1 yield killer from high heat is inability to pollinate. The second yield killer is kernel rejection due to lack of water to keep up with water demand caused by heat."
With cooler temperature from the polar vortex, both pollination and water demand will benefit, he says. Farmers should anticipate full ears of corn pollinated, and very few kernels should be rejected by water demand.
The term "polar vortex" may not be entirely accurate either, Anderson adds.
Last winter, the vortex positioned over the arctic actually moved away and settled over Hudson's Bay. Current conditions have a deepening of the vortex over Hudson's Bay, but this is not due to a piece of an arctic vortex breaking away, he says.
"The effect is the same, but the mechanism is different," he says. "So, it's a polar vortex in effect, though not a polar vortex in process."
See how the polar vortex will affect your area with AgWeb's 10-Day Weather Forecast.
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