The tourist season starts in October and lasts till May.The busiest months are December and January, it is necessary to make a hotel reservation in advance if you plan to go to Dubai at that time.
During summer months the temperature goes up to 48°C (118°F) Sun is all over the year, with short periods between January and March, when you can expect temporary showers.And the yearly rainfall averages just 150mm.

Average Dubai Temperature in Celsius
The coolest month is January, when the average temperature drops to 19°C (66°F), and during winter min temperature stays above 15°C (59°F) at day, and few degrees less at night, so this is the time the pullover may be handy.
For the rest of a year sun hat, water bottle, sunglasses and ski protection oils are necessary, and it is better to avoid moving under the sun of summer months.

Average Dubai Temperature in Fahrenheit
The water temperature in the gulf stays above 20°C (68°F) and goes up to 35°C (95°F) in the summer, when the hotel swimming pool might be more refreshing.