October through April is the obvious window, when daytime temperatures are manageable — typically 20–30°C — and outdoor sightseeing is genuinely pleasant. The winter months (December to February) can feel surprisingly cool in the evenings, particularly up on Jebel Hafeet where temperatures drop further than in the city below. This is when the zoo, the beehive tombs, and the mountain road are at their best.
Summer (June to September) is brutal: temperatures regularly exceed 45°C in the afternoon and the humidity is lower than the coast but still uncomfortable. The oasis provides shade and is worth visiting regardless of season, but Jebel Hafeet and outdoor archaeological sites should be left for early morning or avoided entirely. The date harvest happens in late September and early October — if you time your visit right you can watch the collection in the oasis groves, which is worth going out of your way for. Ramadan brings a distinctive atmosphere — most restaurants close during daylight hours but open in the evenings for iftar, and the pace of the city slows perceptibly.