Meaux is an inland town with a standard northern-French climate: warm summers, mild springs and autumns, and grey, damp winters. There is no bad time to visit the cathedral or the museums, but the experience on the ground varies considerably by season.
Spring (April–May) is the best time for the Bossuet garden: the formal parterres are at their most manicured, and the fruit trees along the Marne bank are in blossom. The light is good for photography of the cathedral's west façade.
Summer (June–August) brings the busiest crowds from Paris, particularly on July and August weekends. The Saturday market swells and the riverbank fills with locals. The heat rarely becomes oppressive — temperatures hover around 24–27°C at peak — and the outdoor café terraces make the most of the long evenings.
Autumn (September–October) is the season for Brie de Meaux: the cheese is at its best after the summer pastures, and the Saturday market has its widest range of produce. Museum queues are shorter than in summer and the cathedral less overrun with school groups.
Winter (November–March) is quiet and occasionally melancholy, but the cathedral interior is atmospheric in low light and the museums are peaceful. The Saturday market continues year-round and is a good reason to get out of Paris on a cold morning.
The First Battle of the Marne is commemorated with ceremonies in September, attracting visitors with an interest in WWI history. The Musée de la Grande Guerre sometimes schedules special events to coincide.