The climate in north and west Sudan is pleasant in winter with temperatures averaging 25^oC but the summers are very hot. Temperatures in Khartoum can reach 48^oC between June and August but it is generally dry. The occasional summer storms can generate the 'habubs'; violent dust storms lasting a few hours. Moving south the temperature range decreases and it is hot (average 25.6^oC) throughout the year with a pronounced wet season, April-October, when the humidity rises to 80-85%. On the Red Sea coast sea breezes temper the worst heat but it can be very humid in summer with sparse (c. 100 mm) rainfall in winter. The vegetation reflects the climate with the Nubian and Libyan deserts in the north passing through coarse grass to scrub, short grass savannah and tall grass savannah to equatorial rain forest. Local variations in this general pattern are found, as for example, near Erkowit, where north-east slopes exposed to damp winds from the Red Sea are covered with dense, evergreen, shrubs. In northern Kordofan and Darfur there is the 'Qoz', a vast area of sand and dunes, up to 30m high, which further north supports a remarkable vegetation of succulents, known locally as Gizu, which provide winter feeding for camels. Acacia Senegal, the species which yields gum arabic, is found in the tall grass area particular in Kordofan.