Reims is a year-round destination with no bad season. Spring (April–June) and autumn (September–October) are the best times: mild temperatures, manageable crowds, and the bonus that October brings the harvest in the vineyards surrounding the city. Summer is busy but not overwhelmingly so — Reims is not the kind of place that becomes impossibly crowded.
The Fêtes Johanniques, a medieval festival held annually in June celebrating Joan of Arc's arrival in Reims in 1429, brings parades and historical re-enactments to the city centre. The Christmas market around the Cathedral in December is one of the better ones in northern France. Winters are cold but not severe; the champagne cellars, at a constant 10°C, are a good reason to visit even in January.