The past summer has been wet and cool. A study of NOAA records shows that around 70% of days this summer has had at least some rainfall with a surplus of about 18" in Knoxville. In July, there were several days of prolonged rainfall and high temperatures that did not even reach 80 degrees. September has been vastly different with plenty of sunshine and unseasonably warm, humid air. This will change on Thursday evening as a cold front pushes through. Along this front there will be the possibility of scattered showers and storms, some strong, before drier air filters in on Friday and through the weekend.
Currently, it looks as though temperatures may not rise above 80 on Saturday with a sunny sky creating a fall-like chill across East Tennessee and the Knoxville area. There should be an abundance of cool, dry air over the weekend.
There could be a return of warm, humid air before summer fades away, but it is clear that fall is right around the corner. This will be our first taste of what is ahead.