Lying just south of the equator Kilimanjaro is affected by the passage of the Intertropical Convergence Zone, which brings with it the main rainy periods. The highest rainfall occurs between mid March and early May, and slightly less between the beginning of November and late December. Maximum rainfall occurs in the forest belt and on the south side of the mountain where it reaches 2000mm. per year. Precipitation on the summit is about 100mm. per year; this coupled with the very porous ash soils results in the Saddle being considered a high altitude desert. Rain and, higher up, snow, can however be encountered at any time of year – even in the driest periods (January, February and September).
Normally the drier seasons are associated with clear, dry weather which can last for weeks on end. The best weather is generally encountered in the mornings, and convectional rainfall, if any, tends to come in mid-afternoon. After long periods of dry weather some of the higher streams dry up.
Temperatures vary considerably with height and time of day. On the plains surrounding Kilimanjaro the average temperature is about 30°C. At 3000m. frosts can be encountered at night while day time temperatures range from 5 to 15°C. Night time temperatures on the summit can be well below freezing.