June to September is the comfortable stretch. Daytime temperatures sit around 20–25°C, the rain stops, the mountains are open, the harbour is busy. July and August are the busiest months — book accommodation early and arrive at popular trailheads (Quarry Rock, the Lynn Canyon parking lot, the Grouse Grind) before nine to find parking.
October and November are wet and dim. The forests are spectacular — fall colour through the cedar-and-maple stands of Lynn Canyon and the Capilano corridor — but rain is constant and the lower slopes can be unpleasant on a multi-day soggy spell.
December to March is the winter ski season. The North Shore mountains receive heavy snowfall — sometimes 12 metres in a season — and Grouse and Seymour both run night skiing. The downside is short daylight hours (sunset at 16:20 in December), wet roads at sea level, and the constant chance of rain that turns to snow at altitude.
April and May are the cherry-blossom and dogwood months. The mountains are still snow-capped, the lower slopes turn green, and the tourist crowds have not yet arrived. May is arguably the prettiest month.