Weather will likely play an important role when you plan your trip to Siwa, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually July and August with an average temp of 86°F, while the coldest months are January and February with an average of 59°F. From January through March, the daytime average is 76°F and the nighttime average is 47°F. Between April and June, temperatures average 98°F during the day and 62°F at night. July through September averages 100°F during the day and 72°F at night. In October-December, the average temperature is 85°F during the day and 51°F at night.