Climate information
The city of Dubai is situated on a coastal strip bordered by desert and gets very hot & humid in the summer. Cooler, more pleasant weather lasts from the end of September to beginning of May (although note that pleasant is relative, which daily temperatures from October to January and March to May still being in the lower 20s Celsius/70s Farenheit).
Be prepared for cold night temperatures. In winter the temperature at night is usually from 10-16 Celsius (50-60 Farenheit). In May, June, July, August and September, the sun is intense and temperatures can touch 45 degrees Celsius in the city and even higher in the desert! The heat coupled with humidity of 60-70 near the coast effectively precludes most activity outdoors for the daylight hours during summer.
December to April generally produces the highest precipitation, which at 10 cm (5 in) still isn't much. Some years yield no more than a few minutes of shower in Dubai. November 2006 brought record rains up to 50 cm of rain with temperatures going down to record lows.