Septembers in Dahab are reliably dry, sunny and very hot. In spite of the reducing daylight, temperatures only fall a little from the heights of July and August, with an average daytime maximum of 36 degrees and an average overnight minimum of 26 degrees. Sea temperatures typically hold up at 28 degrees which makes underwater activities the best bet at this time of year. Rainfall is usually absent during September, and there is an average of 12 hours of bright sunshine per day.
The combination of high outdoor temperatures and balmy sea temperatures makes September a good time of year to try out some of Dahab's famous dive sites. Abu Halal (meaning "Headland of the Crescent Moon") is a popular location, with plenty of different species of coral and fish to marvel at, and 25km deep lagoons for divers to explore. The site is about 4km north of Dahab but facilities are available nearby, including accommodation at the Bedouin Moon Hotel.
Another option is to make use of the Mirage Divers Centre, which is a 5* dive resort near the centre of Dahab which offers a range of diving courses, from beginners' courses to advanced and speciality courses, and a range of diving safaris including camel and boat safaris. Nearby, good accommodation is offered at the Mirage Village Hotel and also at the Blue Beach Club.