Getting back to the question:
From the website of the UAE Embassy in London:
"The dress code in the UAE is generally relaxed however visitors should take note not to wear excessively revealing clothing in public places, as a sign of respect for local culture and customs. Some Emirates adopt a more conservative dress code as well as some hotels. Swimwear is acceptable on the beaches and at hotel swimming pools.
As for the weather requirements, lightweight summer clothing is suitable for most of the year (summer, spring and autumn), though a light sweater or cardigan could be handy when visiting a shopping mall, hotel or restaurant where the temperature might be kept too low to counter the outdoor heat. Slightly heavier clothes are needed for the short winter season, especially in the evening"
http://www.uae-embassy.ae/Embassies/uk/Content/678