The battlefield sites are open year-round but several — Fort de Douaumont, Fort de Vaux, the Mémorial — have shorter winter hours.
April to October is the standard season. May and September are the sweet spot: long days, mild temperatures, low crowds. July and August are warmest but also busiest, particularly with French and German school groups; the Mémorial can be uncomfortably full.
The annual commemoration falls on 21 February (the start of the battle in 1916). The largest events are in centenary years. November is the other peak — for Armistice Day on the 11th, the Ossuary and the cemeteries become focal points for national observance.
Winter is bleak but powerful: bare trees, low light, often a dusting of snow on the shell craters. The Mémorial stays open year-round; many smaller sites close.