Annecy (Lake Annecy) weather in September

Asked to choose between August and September for Lac d'Annecy, the forum picks September: the lake holds its summer warmth and is still very pleasant to swim, and there are far fewer people than in August. The swimming spots round the lake are quiet on weekdays and busier at weekends, and late September thins further - though posters note that as the small boats disappear you still have to watch for the bigger ones. Mornings are the calm part of any day here, whatever the month. The record is the caveat: this is an alpine lake town and September brings 12.3 precipitation days carrying 117.6mm, against 22.7C days, 10C nights and 9.2 hours of sun.

Regulars quote a local weatherman describing this month as generally clear and warm with an occasional real risk of showers, flowers in bloom the genuine draw over March, when snow still covers the surrounding mountains instead. Our row backs that mild, genuinely wet read, 20.6C over 8.1C nights feeling 7C, with a substantial 185.9mm of rain across 17.9 days and a trace of late snow, 2.4cm. Regulars are consistent the lake itself stays genuinely cold this early, June instead the better call for anyone specifically wanting to swim, warm but not hot and less crowded than the following July and August peak. Flowers over snow is the real tradeoff this month makes compared to March. The record: 10.3 hours of sun, an 8.5 kph wind and AQI 44.

Regulars are consistent that the town itself, low in its valley, stays snow-free this month even as the mountains ringing the lake keep real snow cover above roughly 1200-1400m, more at 1800m and up - genuinely two different seasons a short distance apart. Our row backs both halves, a mild 17.2C day over a cold 4.3C night feeling 2C in town, with 114mm of rain across 13.5 days and a real 12.5cm of snow reflecting that higher-elevation total rather than anything falling in town. Regulars are clear this isn't yet an ideal month for serious hiking, with snow still lingering on trails that open properly later in spring. Roads are called reliably clear regardless, kept ploughed through the Alps as a matter of course. The record: humidity 69 percent, 10.3 hours of sun, a 9 kph wind and AQI 43.

The question people ask about June here is whether the lake is warm enough, and the answer has a date on it. Early in the month the water averages about 18.5C, which regulars call too cold to enjoy; by the third week it has come up and swimming is fine. Air is not the constraint - warm but not hot, with afternoon thunderstorms not unusual, which is what our 155.1mm across 16.6 days means at nine millimetres apiece under 11.8 hours of sun. Crowds are the other half: busy but nothing like July and August, though they warn off the lake boat on a summer weekend. Our row gives 26.2C days over 12.4C nights. The record: humidity 74 percent, 15.7 hours of daylight and AQI 50.

July in Annecy is busy and warm, and regulars answer both with the same thing: the lake. It is the cleanest of the big French lakes, swimmable from public beaches all round the town, and the water is what makes a 28.5C day - reading as 30C in our row - a pleasure rather than a trial. The other escape is altitude, since the temperature drops as you climb out of the basin. July and August are the two busiest months, so mornings and the shoulder months are what they suggest for quiet. The number our row adds is rain: 123mm across 13.8 precipitation days, a properly showery Alpine July behind the postcard. Wind is almost absent at 8.7 kph. The record: 14.1C nights, humidity 69 percent, 12.2 hours of sun and AQI 41.