Autumn officially gets underway this weekend but summer is not going down without a fight. Temperatures will remain well above-average Wednesday through Friday. It will be quite humid by September standards, especially Thursday and Friday. Meanwhile, a cold front will slice into the steamy air at the end of the week and this will lead to a good chance for showers and thunderstorms Friday afternoon and evening. There is a chance the thunderstorms could be on the strong side. 

The air behind the front will feel like early autumn, appropriately enough. Cool nights and generally sunny days are in the forecast for the weekend. Rain may return to the Valley early  next week.