Weather: Egypt, Libya, Sudan
Adaptation is the key to life in the Nile Valley, where agriculture has been sustained for millennia. Certainly, without irrigation, crops would not grow so well in the land around Cairo, where the annual rainfall average barely exceeds 20mm/0.8in. South of Egypt's north coast and populous northeast corner, the climate is relatively uniform. From early June into September, rains are absent and clouds are scarce. Temperatures top 32°C/90°F virtually everywhere except along the eastern Mediterranean coast. South of Luxor, summer highs typically exceed 38°C/100°F. Nights are toasty, too, although the lower Nile delta benefits from the persistent north breeze that funnels in Mediterranean-cooled air. Autumn is fairly uneventful, although it's the most likely time for a stray thunderstorm across the north. December or January may be the best time for desert trekking: days are sunny and warm and nights are crisp. Rains are usually limited to the north coast, especially during winter. Alexandria may get a chilly soaking about 1 out of 4 days in December and January. An occasional maritime storm can bring a day or two of coolness and light rain as far south as Cairo, and snow may briefly coat the north slopes of the Sinai peaks. Throughout the cooler months, Cairo and other valley sites often see night and morning fog and smog. As the Sahara heats up in spring, Mediterranean storms are drawn southward int the desert, where they kick up little rain – but great clouds of dust – before moving across the Nile valley. These khamsin storms (ghibili in Libya, irifi in Sudan) may strike several times a month, often preceded by a day of pictureperfect weather. Temperatures during khamsins can exceed 45°C/113°F, and relative humidities may tumble below 5 percent. The few khamsins that strike in February and March are typically less superheated than their late-spring counterparts, although they may carry even more dust. A different kind of windstorm plagues central Sudan in the late spring and summer, as lowrainfall thunderstorms generate haboobs. These squally blasts (over a dozen strike during an average year at Khartoum) can blow at hurricane force for a half-hour or so ahead of a quick shot of rain. Otherwise, Sudan's weather fits the Sahel pattern: bone-dry in the north (as in virtually all of Libya, except its Mediterranean coast), with a summer wet season that's progressively longer in duration toward the south. The average highs in blistering Khartoum exceed 38°C/100°F from March into October.