Weather end of september in provence

When I've been in Provence in September, the weather has been quite nice. Remember, this is the South of France. However, it is what it is, and no one can predict for certain what the weather will be. You can always Google the weather forecast a week or so before arrival. I'd be prepared with a light rain jacket and a sweater for layering.

I'd look at a live stream weather channel two days before packing anything.
It will probably be foggy and chilly, but you never know.

Our few visits to Provence have been late Sept into early Oct - for the most part, weather was fine - warm and sunny. We did have one day of extremely heavy rains and local flooding - that was when there was bad flooding and deaths in Cannes in 2014. We were two days away from going to that area. We had to cut our day short as it rained so hard, we could barely see the road to drive on - luckily, we were at an airbnb with use of the kitchen so we went back early and I cooked supper. Otherwise, the weather was perfect.

The Weather Underground site has an option for the weather history of a certain location during a certain time period such as a given date in September. Here's the page for Marseille history
https://www.wunderground.com/history/airport/LFML/2017/9/16/DailyHistory.html

great suggestions ...thanks to all.

We were in this general area last fall in September and it was very warm much of the time. I spent a lot of time in a sleeveless blouse and lightweight skirt and sandals. It ranged from hot to warm.

I agree with Jane. We were there about the same time and found the same weather. We were on a Viking cruise. However someone up river had a lot of rain because we could not get under one of the bridges on the last day because of high water. So it rained somewhere but not where we were.