There are two rainy seasons that you should probably avoid to make the most of the good weather in Kenya. The short rains are in November and the long rains start at the end of March and go through to the end of May. Although, having said that, we will add that its not really that big a deal, people are used to it and manage to carry on rain or no, and sliding around in a Land Rover in and out of the mud can actually be a lot of fun. August and October are just about the best times but to see the wildebeest migration in the Maasai Mara you will want to come around the end of July through September.