November to March is the only sensible time to visit Dubai if outdoor activity is on your agenda. Average daytime temperatures are 24–28°C, evenings are pleasantly cool, and the city is at its most energetic — the Dubai Shopping Festival runs through January and February, the Dubai World Cup horse race is in March, and the Dubai Tennis Championships and food festivals fill the calendar.
April and October are shoulder months: warm and often humid, but manageable. From May to September, outdoor life effectively stops. Temperatures reach 40–45°C and humidity near the coast can push the heat index well above 50°C. The city continues indoors — malls, hotels, and air-conditioned everything — and visitor numbers are lower, with corresponding discounts on hotel rates.
Ramadan, which shifts by about 11 days each year according to the Islamic calendar, is an interesting if logistically complex time to visit. Eating and drinking in public during daylight hours is prohibited. Most hotels provide screened areas. After sunset, the city comes alive for Iftar (the fast-breaking meal), and late-night dining and street activity have a festive quality. Many bars and clubs close or restrict service.