Kenya month by month, honestly
July to October is the dry season and the migration window in the Maasai Mara. Grass is short, animals gather at water, and the river crossings are possible on any day in that period. It is also the busiest and most expensive time, which is why the rates above are quoted for August and September.
January to March is the other strong window. Skies are clear, the parks are quieter, calving means plenty of predator activity, and Amboseli is at its best for Kilimanjaro views.
April, May and part of November are the long and short rains. Roads get harder, some camps close, and rates fall a long way. If afternoon storms do not bother you, the landscape is at its most beautiful and you will share sightings with almost nobody.