A nice chart that speaks for itself (based on temperatures and rainfall):
Source: thesunnylife.net
Many people offered useful advice but I would like to stress that both climate and things to do will depend a lot on the area you are considering. The summer (July-August) offers the warmest temperatures and the best chances of sun but that’s also the season with the most visitors and long waiting times for some attractions.
I also occasionally find the weather too hot so that I would recommend considering coming in the Spring (April-June). Many vacation-oriented facilities will be opened after Easter, the weather is often very nice and you can witness the “normal” life without the high number of tourists and reduced activity from the Summer. Hotels or rentals will also be less expensive. At the same time, there is a significant risk of bad weather, especially in the North and West of the country and in some places (e.g. mountain resorts), this is still the off-season with absolutely nothing going on.
It actually all depends on where you intend to go and what you want to do. France has very strong regional differences, both in weather and touristic periods.
For Paris, I’d recommend visiting it in August, where most locals have left the town. It’ll be full of tourists, but there will still be less people than in other times of the year, and the weather will be good. Then, from Paris, you can go pretty much anywhere very easily by train.
Regarding festivals, Paris has a lot of them all year round. The rest of the country usually is much more concentrated over the summer period.
To give another example of a touristic destination: on the contrary, I’d recommend visiting the Riviera just a bit off-season, i.e. beginning of May – half of June or September – October. Weather will still be lovely, but it will be substantially more livable regarding crowded beaches and small towns than between June and August.
In Paris the 4th weekend in November, by far. Then there is the annual Salon du vin of the independent “vignerons”. This event is massive and really worth a visit. Thousands of wine farmers present their latest harvest for you to taste.
You can get an impression of the event here
The best time to visit France is in the spring (Apr-June) or fall (Sept-Nov), July and August are the worst for crowds. Visit France during Spring or fall you can enjoy your trip at that time.
I have heard that many people in France take their holidays during August, and hence many shops/business will be closed and many tourist accomodations will be busy and booked out.
I spent ~ 2 weeks motorbike around France in the first 2 weeks of September, and didn’t have a problem with booking accomodation, I was able to just turn up at 5pm and have a room for the night. The weather was also still quite warm.
I’d recommend either May or September. In particular, Paris is going to be overrun with crowds during June, July, and August with students and families that are only able to travel during those months.
I would recommend summer.
The weather is warm but not too hot, less than in Italy or Japan. See this minimum/maximum graph in Nice (in Celsius, 25°C=77°F):
During summer touristic places are open everywhere, even in the South, the warmer the better.
During summer people working in Paris leave for the South, but Paris still has a lot of activities, even more than during other seasons.
Most festivals happen during summer, especially countryside ones (list).
Other seasons can be rainy but summer usually is not. See the low rain stats during July/August:
Credit:stackoverflow.com‘