When to come — and when to absolutely avoid
By season
Quietest: Mid-January to mid-March and the first three weeks of November — Paris in the off-season filters out casual day-trippers. Cold, often grey, but the Impressionist galleries are at their most peaceful.
Busiest: June, July and August (especially the run-up to Bastille Day on 14 July), plus the Christmas–New Year week. Saturdays from April to October are always packed. Avoid the first Sunday of the month unless you arrive at opening — free entry brings the largest crowds of the year.
By day of the week
Tuesday and Wednesday mornings are calmest. Saturdays and Sundays are always busy. Thursday late nights have a different, more relaxed crowd — fewer tour groups, more locals on date night.
By time of day
The first slot at 09:30 and slots after 16:30 are noticeably quieter than the 11:00–14:00 peak when most coach tour and cruise-passenger groups arrive. The Impressionist gallery on level 5 is at its calmest in the first 30 minutes after opening or in the final hour before close.