last year my wife and I spent September at le Bugue KEYCAMP in the Dordogne. Temperature during the day was up to 33C but at night it could be VERY cold! Also there is a tendency for thunderstorms due to the high ambient temperatures. While there you must visit the medieval town of SARLAT, especially on saturday when they have a HUGE market.
If you are going to KEYCAMP at Le Bugue, bear in mind that the instructions from KEYCAMP for the last leg of the journey are incorrect! Instead of taking the side roads from Perigeaux as suggested take the main road to Le Bugue and look out for the sign to "St. Avits" on the right about 18 miles down that road. The camp site is about 5 kilometeres down this route. The instructions from KEYCAMP take you a right dance around the country lanes! We told the camp attendants about this and they admitted the problem.