Some say that November and April are the best months to visit Red Sea. Weather is perfect, with average 28°C air and 23°C water temperature. But even in January you can swim, snorkel or dive so you can enjoy Red Sea all year long.

Although average temperature very between 21°C durring colder months, there are many days with much higher temperature. On such days, you can spend whole day on the sun without getting burned.
Wind is a bit stronger sometimes, and although it cause chilly feeling, it's not enough to stop people from swimming and snorkeling. During summer months temperatures are higher but dry weather make it a lot easier.