The annual chestnut festivals in Collobrières are taking place on the three Sundays of the 14th, 21st and 28th of October. Collobrières is deep in the forested hills of the Maures, west of Saint Tropez and northeast of Toulon and Hyères. This is excellent country for hiking, and a visit to the Carthusian monastery "Chartreuse de la Verne".
Also on Sunday the 21st are chestnut festivals in Camps-la-Source (3 km southeast of Brignoles), Gonfaron (with the famous "Flying Donkey"), Les Meyons (10 km south of Le Luc), Tanneron (in the hills west of Cannes), and Valdeblore La Bolline (in the mountains of the Alpes Maritimes, between St Martin-Vésubie and St Sauveur-sur-Tinée).
There are, of course, other October chestnut festivals in other parts of France.