Richmond is a year-round destination but the upper Dales need a forgiving weather mood. April to early October is the safe window, with the longest evenings in June and the most reliable warmth in late July and August. Heather is in flower across the surrounding moors in August, which is the most photogenic time on the high ground.
September and October bring autumn colour to the river woods and far fewer visitors. November to March is genuinely quiet — many of the local cafes and smaller museums close for parts of the winter — but Richmond Castle is open all year, the Georgian Theatre runs a Christmas pantomime that books out months in advance, and a frost-rimed walk along the Swale has its own quiet appeal.
The Richmond Live music festival in mid-July and the Richmond Walking and Book Festival in late September are the two events worth timing a visit around.