Trabzon is one of the wettest cities in Turkey — the Black Sea coast receives heavy rainfall year-round, with the wettest months typically being November through January. This is not a deterrent but a fact to plan around: even in summer, rain is possible on any given day.
The best weather is from May through September, when temperatures are in the 20s and the coast and mountains are accessible. Late spring (May–June) is particularly attractive when the highland meadows are green and the rhododendrons flower. Summer weekends see Turkish domestic tourists arriving from drier inland cities. Winter is mild enough for the city itself but the mountain roads to sites like Sumela Monastery can be icy or snow-closed from November through March.