In reply to mypyrex:
There'll always be early snow storms in the Alps - September/ October time. However, these will often be followed by weeks and weeks of great clear weather which can extend into December (or not!) - the snow often stays on the northerly aspects and forms a base for the winter though if it's exceptionally mild it can disappear. I've had some of my most memorable climbing days in October and November, climbing on crags at 2500m and more in light summer clothes. No one around, the place to ourselves. Of course the days are shorter and the nights are colder, but that's the price you pay... We even made the FA of this route in the valley of Tré les Eaux above Vallorcine on the 2nd December in glorious sunshine:
Alors, heureuse...? (6b+) Snowed 60cm the next day, mind...