The most important question to ask before traveling to Dubai is, "How hot is it?" From mid-October to mid-April, Dubai's weather is ideal with moderate temperatures and blue skies. From mid-April to mid-October, the climate becomes less bearable, with temperatures routinely exceeding 100°F (37°C) and humidity often hitting 95% or more from June through September. It's only slightly less hot and humid in the immediate surrounding months.
Another question to consider is whether to visit during Ramadan (the dates for which change each year based on the Islamic calendar). It's a fascinating period in Dubai but one in which businesses often have limited hours during the day, many restaurants don't open until night, and the majority of bars and nightclubs remain closed. Ramadan will take place in August in 2011 and 2012, which coincides with the hottest months of the year.
Peak Travel Seasons -- October to May is high season, with December and January the busiest months. Hotels also fill up for the Dubai Shopping Festival in February and the Dubai World Cup in March. The city is somewhat quieter during the heat of summer, when hotels and many other hospitality services reduce prices in order to lure more visitors.
Climate -- Dubai has a sub-tropical, arid climate and is sunny most of the year. Rainfall is infrequent, falling only in the winter months. The city is ill-prepared for downpours, and when they happen, chaos on the roads ensues but is short-lived. Flash floods are possible in the wadis (desert oases). Temperatures range from a low of 50°F (10°C) in January and February to a high of 120°F (49°C) in July and August. Even the sea is hot in summer, approaching 100°F (37°C). It's usually too hot to sit outside in the summer months, except in swimming pools that actually have to be cooled so they don't turn into nature-made Jacuzzis. Sandstorms are most common in March and April, but can occur whenever the wind kicks up.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.