Tanzania has generally comfortable, tropical climate year-round, although there are significant regional variations. Along the warmer and humid coast, the climate is determined in large part by the monsoon winds, which bring rains in two major periods. During the long rains, from mid-March to May, it rains heavily almost every day, although seldom for the whole day, and the air can get unpleasantly sticky. The lighter short rains fall during November, December and sometimes into January. Inland, altitude is a major determinant of conditions; you will need a jacket early morning and evening, especially in high land areas.