Generally, from January to March, and from July to October, it’s hot and dry. From April to June and from November to December, it’s hot and wet. These wet periods are called the ‘long rains’ and the ‘short rains’, respectively. Rains usually come in heavy but short outbursts, especially in the afternoon and evening.
However, January to March are on average the hottest and July to August the coolest periods (though the differences aren’t big). So it’s exactly the opposite from North America and Europe.
Climate per region
The climate at the coast, where many tourists stay, is hotter and more humid than inlands. In the coastal town of Mombasa (17 metres above sea level), the average day temperature is the highest in January and February at 31 degrees Celcius (88 degrees Fahrenheit) and the lowest in July and August with 27 degrees C (81 degrees F).
The two main tourist seasons tie in with the dry periods: December-January and to a lesser extent July-August. One big advantage is that in the dry seasons, wildlife can be spotted easily as animals are concentrated along the more scare water sources. July and August are usually the best periods for ‘game drives’ (driving around in natural parks to spot wildlife). During the ‘long rains’ (April to June) the mountain parks are sometimes closed because the tracks are muddy and undriveable.
However, there are also advantages in travelling in the rainy season. There are less tourists and hotel and other prices are lower. And as noted above, during the rainy seasons the rains are often heavy but short.
Kenya Climate - Weather forecasts at the Kenya Meteorological Office