The good months are November to March, with daytime temperatures of 22–28°C and cool, dry evenings. December and January are the busiest tourism months — beaches fill, hotel rates spike, and the mountain road can have traffic on weekends. February is the sweet spot: warm enough for the beach, cool enough to hike, and rates start dropping after the New Year peak.
April and October are still pleasant but hotter (30–35°C). From May to September the daytime heat climbs to 40–45°C with high humidity on the coast — beach time is essentially impossible in the middle of the day, and most outdoor activity has to be done at dawn or after sunset. The trade-off is hotel prices that drop by more than half. December's Ras Al Khaimah New Year fireworks are the largest in the world by some metrics — worth being on Al Marjan that night if you are in town.