The climate is characterized by high temperatures, especially at the end of the dry season. The humidity, which increases as one moves south, ranges from a winter lows of 12% to 45% to a rainy season highs of 68% to 96%. The harmattan, a dry east wind, brings with it spells of considerable heat from March to May, when maximum temperatures range from 40° C to 48° C (104° to 119° F ); from May to October, the climate is hot and wet, and from November to March, comfortable and dry. January temperatures range from 7° C to 13° C (44° to 55° F ). Average annual rainfall varies from 115 cm (45 in) in the southwest to less than 25 cm (10 in) in the extreme north and northeast. The rainy season lasts from four months in the northeast to six months in the southwest, from May through October. From 1969 to 1974, Burkina Faso suffered from drought, especially in the north, which is in the semiarid Sahel zone.