IT'S NOT THE HEAT, IT'S THE HUMIDITY
Right now it's kind of both that's going to get you. But the humidity is running high.. something that's pretty typical this time of year. In order to discuss humidity we have to talk about the dew point temperature. Here's an explanation of the dew point from the National Weather Service in La Crosse:
"The dew point is the temperature the air needs to be cooled to (at constant pressure) in order to achieve a relative humidity (RH) of 100%. At this point the air cannot hold more water in the gas form. If the air were to be cooled even more, water vapor would have to come out of the atmosphere in the liquid form, usually as fog or precipitation.
The higher the dew point rises, the greater the amount of moisture in the air. This directly affects how "comfortable" it will feel outside."
This is a graphic from WeatherWorks, which shows the correlation of the dew point temperatures to how it feels outside. When dew points get to near 80 degrees (which can happen in the heat of the summer and with full grown corn around) it feel miserable outside.
Saturday was one of those days where it was unpleasant and gross outside. The dew points in the evening were still very high!
Gross. That's the case pretty much everywhere east of the Rockies. And that's going to be the case over the next few days. A boundary is going to be hanging around which will keep the humidity high and in turn keep moisture levels and rain chances elevated in the Upper Midwest.
First off Sunday will be warm and muggy.
The boundary we were discussing earlier will then lead to scattered thunderstorms Sunday afternoon and evening. The Storm Prediction Center has a slight risk of severe weather in western Iowa for Sunday:
There is some uncertainty with the timing and placement of storms but storms will be capable of damaging winds, large hail and tornadoes. Here's a snapshot of the hi-resolution NAM Sunday afternoon:
The pattern will remain active, warm, and muggy through much of next week as well.