I know I can check for daily averages online however for those who have been in Provence mid September do you have any suggestions on what is appropriate. Should I even plan on taking my capris or stick to long pants/skirts? Will I need a jacket? What about a bathing suit? (The b&b's have pools). Does the weather tend to change drastically at that time of year. At home it can be hot and sunny and turn very cool and rainy the next day. Is that likely to happen there?

Check to see if the B&B's will close their pools before you arrive.

Other than that, the weather should be reasonably good. It can rain and be cold anytime (the tour de france had cold rainy weather mid July in Toulouse) but don't plan for that. Take a rain jacket and sweater for layering but don't bring a lot of cold weather clothes. Capris should be perfect.

I was in Provence last September and found it to be very hot during the days and as soon as the sun went down to be a lot cooler. Capris and t-shirts for the days or a light skirt. At night I wore long cotton pants and a 3/4 sleeve type top and usually a jacket of some description, either a denim jacket or a little fleece zip up top. The night the mistral came through it was freezing!!! Unbelievable - I had read about the mistral and thought they were exaggerating but not so!!

Take sun screen and sunnies and a hat for the day. If you are doing any form of exercise, ie bike riding, horse riding, canoeing on the Gorge Verdon (good fun time) then you will need shorts. I threw in one pair and wore them only for these activities, others at my course wore shorts during the day as well.

I was there the first three weeks of September.
Schnauzer - hope this helps.

I can't imagine any hotel or B&B in Provence shutting a pool down until at least mid-October. September is still prime pool time.

There are no guarantees, of course, but it's likely to be hot, perhaps very hot, during the day in mid-September. If you're lucky it will be cool enough in the evening to wear a light jacket.

Daytime temperatures are still around 28°-30° in September.