The best time to visit Paris is in the spring (Apr-June) or fall (Sept-Nov), when things are easier to come by -- from Métro seats to good-tempered waiters. The weather is temperate year-round. July and August are the worst for crowds. Parisians desert their city, leaving it to the tourists.
Hotels used to charge off-season rates during the cold, rainy period from November to February; now, they're often packed with business travelers, trade fairs, and winter tour groups, and hoteliers have less incentive to offer discounts. Airfares are still cheaper during these months, and more promotions are available. They rise in the spring and fall, peaking in the summer, when tickets cost the most.
In even-numbered years, don't come to Paris during the first 2 weeks of October without a confirmed hotel room. The weather's fine, but the city is jammed for the auto show.
Weather -- France's weather varies from region to region and even from town to town. Despite its latitude, Paris never gets very cold; snow is rare. The hands-down winner for wetness is Brittany. Brest (known for the mold -- probably caused by the constant damp -- that adds flavor to its blue cheeses) receives a staggering amount of rain between October and December. Rain usually falls in a steady, foggy drizzle and rarely lasts more than a day. May is the driest month.
The Mediterranean coast in the south has the driest climate. When it does rain, it's heaviest in spring and autumn. (Cannes sometimes receives more rainfall than Paris.) Summers are comfortably dry -- beneficial to humans but deadly to vegetation, which (unless it's irrigated) often dries and burns up in the parched months.
Provence dreads le mistral (an unrelenting, hot wind), which most often blows in the winter for a few days but can last for up to 2 weeks.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.