The best time to visit Paris is from June to August and September to October. Both summer and fall have its ups and downs. From June to August the weather in Paris is just about parfait (perfect). Average highs are in the high 70s and there are long days of sunshine. Unfortunately, summer is also the most crowded time – and the most expensive. For lower travel rates and significantly shorter lines at attractions, plan a visit in the fall.
The seasonal foliage is known to stun, though the city's spring blooms are pretty famous too. If a travel deal is all that you're after, a visit during the winter will surely shave off travel expenses. Keep in mind though that Paris is one of the most visited cities in the world, seeing upward of 30 million travelers yearly. So no matter what time you visit, there will always be tourists and some crowds.