Kenya's climate varies widely from region to region. Generally, Kenya is considered to be a dry country, with more than 75% of its area classified as either arid or semi-arid. Only 20% of its ground area is considered viable for agriculture. In the interior sections of the country, rainfall totals and average temperatures are closely related to altitude changes, with variations induced by local topography. Generally, the climate is warm and humid along the coast, cool and humid in the central highlands, and hot and dry in the north and east.

Across most of the country, rainfall is strongly seasonal, although its pattern, timing and extent vary greatly from place to place and from year to year. Differences in temperature vary predictably with altitude. Frost regularly occurs at elevations of 10,000 feet (3,000 meters), and occasionally at elevations as low as 7,800 feet (2,400 meters). There is permanent ice and snow at Mount Kenya's summit. The hottest parts of the country are the arid northeast and the area west of Lake Turkana, where average daytime temperatures range as high as 93° F (34° C).

The main tourist season is in January and February, since the hot, dry weather at this time of year is generally considered to be the most pleasant. It is also the time of year that Kenya's magnificent bird life congregates on the shores of the Rift Valley lakes in their greatest numbers. But any time of year is a good time to visit Kenya. The months of June through September are considered the "shoulder season," because the weather is still dry. The rains generally fall between March and May (and, to a lesser extent, from October through December). During these months, things are much quieter, rooms are available and prices tend to be lower. And the rains typically have little impact on the travelers' ability to get around.