Much warmer and more humid conditions will gradually return to the region for late week and the weekend. Expected high temperatures will build from 70s and lower 80s today and Thursday, to upper 80s and 90s for Saturday and Sunday. With southerly flow returning more moisture, humidity levels will also be increasing, leading to heat index readings from 95 to 105 through the Missouri Valley on Friday, in much of the area Saturday, and across northwest Iowa on Sunday. During the transition late Thursday and Thursday night, thunderstorms will become more likely, and some severe storms are possible with large hail and damaging wind.
For Sioux Falls, the expected high temperature on Saturday would mark the first 90 degree reading since June 20, and only the 5th 90 degree reading of the year.