It is possible to trek Kilimanjaro all-year-round. However, certain months are characterized by colder weather, more rain and potentially loads of snow on the summit.
There are two distinct trekking seasons which constitute the best time to climb Kilimanjaro. They are January-March and June-October.
January-March is generally colder than June-October and there is a higher probability of encountering snow on the summit. For some this might be seen as a negative, but the benefits of a January-March trek is that the slopes are often quieter at this time of the year.
The June-October trekking season coincides with the summer holidays in Europe and Northern America and hence certain routes are often quite busy.
March, April and November are the wettest months on Kilimanjaro, and not ideal of trekking although some clients wishes to do the trekking at the time of a bit challenge.
Snow fall and cold temperatures are common during December-May.