Here's Why It's Been So Humid Lately

As the Sioux Empire waits out the end of this week's heatwave, one wonders where all this comes from? We've had air temperatures into the 90s and thick, heavy humidity pushing the heat index over 100.

What Exactly Is ‘Heat Index’?

What factors combine to create this soul melting outside oven? The National Weather Service says it's partially a combination of two factors. One man-made and one atmosphere related.

The atmosphere related factor is the flow of warm, moist air that is streaming north from the Gulf of Mexico. High pressure in southern North America is pushing that humid air north into the Midwest.

NWS Forcast 072216

The man-made factor is corn. In parts of the country that have huge areas of corn, the local humidity can be higher. Know as 'corn sweat' it's really called evapotranspiration. The plant takes moisture from the ground and some of that evaporates off of leaves. With all the corn planted in the country this year, that's a lot of moisture added to the air. According to the USDA, around 94.1 million acres of corn have been planted across the country this year, one of the highest number since 1944. That will sure push those dew points up.

Corn acreage by county in 2015 (USDA)