But why did it feel so muggy outside? It's because our dew point temperatures were very high. Dew point temperatures (exact measure of the amount of moisture we have in the atmosphere) were in the low 70's. That's an extremely moist air mass - more like the tropics. There's a reason why our dew points were so high Wednesday and it has to do with the heavy rainfall from the night before.
There are several ways for the dew point temperature to increase in the Midwest. A high moisture air mass is 'brought in' from the south, typically the Gulf, evapotranspiration from the surrounding corn crops during the summer, and rainfall.
We received quite a bit of rain Tuesday evening and overnight. And most of that moisture soaked into the ground, although there were reports of flooding. With the now moisture rich ground, the full sun we had Wednesday afternoon allowed that moisture to evaporate from the soil and into the atmosphere. We were essentially adding moisture into the atmosphere from our ground. The hotter it got, the more moisture was able to evaporate causing our dew point temperature to rise during the afternoon.
Wednesday evening a cold front tied to an area of low pressure in Wisconsin will pass through. Winds will gradually shift around to the west and then northwest by Thursday morning. Northwest winds typically bring drier air so our dew point temperature will decrease from the low 70's into the low to mid 60's Thursday. It'll probably still feel a little humid Thursday, but shouldn't be quite as oppressive as Wednesday afternoon.
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