Temperatures Tuesday afternoon warmed into the mid and upper 80s, with Rockford reaching 90 degrees. While temperatures will take a little bit of a dip Wednesday following the passage of a cold front, we’ll feel temperatures rise in a big way by the end of the week and weekend.
The cold front passing through Tuesday evening will remain west and south of the Stateline Wednesday. This will allow us to hold on to a northeast breeze during the afternoon with high temperatures falling about 10 degrees cooler than Tuesday’s high; right around 80 degrees. Low pressure passing to the north Thursday will draw the front back north as a warm front during the morning and afternoon.
The front won’t completely clear the region Thursday, so highs may fall just shy of the 90 degree mark, warming into the upper 80s. A few showers and thunderstorms are possible during the morning, mostly to the north. But with the heating of the day and a few upper level disturbances rippling through within the northwest flow during the afternoon, widely scattered thunderstorms will be possible.
By Friday the front will have pulled north and northeast pushing high temperatures into the low 90s and the heat index into the mid and upper 90s. Saturday and Sunday look to be the hottest days out of the heat wave stretch with temperatures holding into the low 90s, but the heat index possibly reaching 100 degrees, if not more.
Dew point temperatures will also warm during that time climbing near 70 degrees, if not higher, for most through the weekend. But the wind isn’t the only thing bringing those numbers up. The maturing corn crop will also help by adding more moisture into the atmosphere, especially to the south. That’s because the evapotranspiration rate is reaching its peak; which is typically mid to late July through mid August. Evapotranspiration is the combination of evaporation, moisture coming from the soil, and transpiration, moisture coming from the leaves of plants. Evapotranspiration will be highest south of Rockford where not only are there more corn fields, but also where there is a little more moisture due to more rain. Over the moderate to extreme drought conditions in northern Illinois and southern Wisconsin the evapotranspiration rate may not be quite as high. Either way, a prolonged period of heat and humidity will set in and could begin to take a toll on the body by the end of the weekend and early next week.