You are more likely to gain the summit in warm and dry weather since cold, rain, ice, snow and mud demand a lot from your body. They make tracks and paths slippery and deplete your energy levels. From mid-March to end of May, the long rainy season increases climbing hazards. Visibility is poor, but you have the slopes to yourselves. Lightning is every present and chancy. It is colder from June to August but the driest period on the mountains which are also highly favorable trekking months, and perfect again in September, which is warm and dry too, and, not surprisingly, another very popular and busiest time as it meets up with the prime wildebeest migration season in Masai Mara and northern Serengeti. The school holiday season from June to August welcomes many families. End of October and November is the start of the short rainy season when clear skies are the norm at dawn and dusk. By end of December, the short rains dusts off with sporadic showers through January onwards with clear mountainous vistas perfect for photography but humid and advantageously less colder than from June to August.