Kilimanjaro: While Kilimanjaro can be climbed at any time during the year, the two primary climbing seasons coincide with the mountain’s two dry seasons (even during the dry seasons, occasional inclement weather exists). The January – March dry season is the colder season and also has a much higher probability of snow on the summit. Days tend to be clear with only an occasional brief shower. June – October is the second dry season, which tends to be warmer. Clouds tend to hang around the tree-line, but once above the skies are typically clear and blue with only a minimal chance of precipitation.
While on the mountain, temperatures will vary significantly from hot and sunny during the day at lower elevations, to below freezing temperatures and wind during the night-time ascent of Uhuru Peak. All of your gear and clothing should be waterproof and appropriate for cold and wet weather travel. Rain is possible even during the dry seasons, and snow is possible at higher elevations. You should pack your clothing to allow layering or warmer layers as temperatures drop.
Safari: Tanzania’s climate is determined in large part by its monsoon winds, which bring two rainy periods. The long rains (masika) are from mid-March through May when it rains heavily almost every day (though not necessarily all day). The short rains (mvuli) are from November through early January. In between are the dry seasons which experience occasional rain, so be prepared for rain anytime of year.
The warmest months are December to March and the coolest months are June to October. The coastal areas tend to be tropical with high humidity, while the interior plateau tends to be more arid and cooler. And of course, higher altitudes mean cooler temperatures.