Last week's weather gave us a great preview of fall, with temperatures in the 60's, or 10 to 15 degrees below average. The rest of this week features the exact opposite.
Highs have been in the 80's for two days in a row, and that streak should continue through the end of the week. By Friday, highs may be well into the middle 80's, or at least 10 degrees above average.
This isn't uncommon for September. Over the last 20 years, Rockford has averaged 12 days in the 80's during September, and 2 days in the 90's! The weather won't be in the 90's over the upcoming extended warm stretch, but conditions do get a little muggy. The humidity looks to be higher starting Friday and lasting into the weekend, so be ready for the heat index to jump into the upper 80's. With the higher "feels like" conditions, you may want to have the A/C on at times Friday and into the weekend.