Yerevan has a sharply continental climate: hot, dry summers and cold, dry winters, with very little rain in any season. May, June, September, and early October are the best months — warm but not punishing, with clear skies and Mount Ararat usually visible from the city. In July and August the daytime temperature regularly tops 35°C and the centre can feel exhausting in the middle of the day; locals flee to Lake Sevan or the cooler highlands.
Winter is cold (down to -15°C in January) and the Caucasus light is short. December's Christmas market on Republic Square and the New Year's celebrations are atmospheric but expect snow and slush.
Worth timing a trip around: the Yerevan Wine Days in early June, the Golden Apricot International Film Festival in mid-July, and the HIGH FEST performing-arts festival in October.