Sharm el-Sheikh, where it is

In Sharm el-Sheikh, an Egyptian resort on the Red Sea, the climate is subtropical desert, with very mild winters and very hot summers.
Here are the average temperatures.
Sharm el Sheikh - Average temperatures
Min (°C)131416202427272827231915
Max (°C)222225303437383835322723
Min (°F)555761687581818281736659
Max (°F)72727786939910010095908173

The rains are very rare: in practice, it never rains. Here is the average precipitation.
Sharm el Sheikh - Average precipitation

In winter, the temperatures are very mild, and the sky is usually clear. The rains are very rare also in this season. Every now and then, a bit of cold air can arrive, and can lower the night temperature below 10 °C (50 °F), from December to February and more rarely in March.

Spring is pleasantly warm at the beginning, in March, and it becomes hot already in April, when the weather is similar to the Mediterranean summer, while by May the heat is intense.

Summer, from mid-May to September, is really hot, with the sun always shining and very high temperatures. It is true that the air is usually dry, especially on hotter days, but the heat is intense, and the temperature exceeds quite often 40 °C (104 °F), with peaks of 45 °C (113 °F).

Autumn, in October and November, is hot and sunny; sometimes in early October the heat is still intense, then the temperature gradually decreases.

The amount of sunshine in Sharm is always great: the sun shines all year round. The sun can be obscured for a few hours by sand storms, while at times some cloud banks may pass over the area from November to February.
Sharm el Sheikh - Sunshine

Every now and then, in Sharm the Khamsin can blow, a hot and dry wind that raises dust storms, and blows especially between March and May.

Sharm el-Sheikh

The sea is very warm from June to October, so as to make possible long swims: the sea temperature reaches 28 °C (82 °F) in August and September. In winter, the sea is a bit cool, but after all it's not impossible for swimming, since the temperature drops to 21 °C (70 °F) in February and March.
Here are the average sea temperatures.
Sharm el Sheikh - Sea temperature
Temp (°C)222121232426272828272524
Temp (°F)727070737579818282817775

Best Time

The best times to go to Sharm el-Sheikh, for swimming and diving, are the month of April, and from mid-October to mid-November. Summer, from mid-May to September, is actually quite hot, and while the sea is pleasantly warm (especially in August and September) and you can enjoy long dives, it can be difficult to get around and to sunbathe during the day.
In winter, a stay in this town can be enjoyable, and the temperature is often sufficient for sunbathing, however, the days are quite short and sometimes it can be a bit cool, and as mentioned the sea is a bit cool as well.