The single most important factor in deciding when to visit France is tourism itself. As most French people take their holidays in their own country, it’s as well to consider avoiding the main French holiday periods – mid-July to the end of August. At this time almost the entire country closes down, except for the tourist industry itself. Easter, too, is a bad time for Paris: half of Europe’s schoolchildren seem to descend on the city. For the same reasons, ski buffs should keep in mind the February school ski break. And no one who values life, limb and sanity should ever be caught on the roads during the last weekend of July or August, and least of all on the weekend of August 15.
Generally speaking, climate needn’t be a major consideration in planning when to go. Northern France, like nearby Britain, is wet and unpredictable. Paris has a marginally better climate than New York, rarely reaching the extremes of heat and cold of that city, but only south of the Loire does the weather become significantly warmer. West coast weather, even in the south, is tempered by the proximity of the Atlantic, and is subject to violent storms and close thundery days even in summer. The centre and east, as you leave the coasts behind, have a more continental climate, with colder winters and hotter summers. The most reliable weather is along and behind the Mediterranean coastline and on Corsica, where winter is short and summer long and hot.