It's July so it should be expected that the nice, comfortable days won't last. And that is going to be the case for the upcoming week, and possibly for the remainder of the month.
Thunderstorms have once again developed over North Dakota and will ride right down the edge of the upper level ridge by Monday morning. The only difference is that a warm front will be pulling through Northern Illinois and Southern Wisconsin overnight. This should help to focus the storm activity more to the north over Wisconsin than to our west.
Following the warm front temperatures will quickly warm over highs we had this weekend. Pending any major cloud cover Monday, high temperatures have a good chance of reaching 90 degrees.
Following the front there will be a brief break in the humidity Thursday and Friday, but it returns late in the upcoming weekend and could be in full force by next week.