It is possible to climb Kilimanjaro all year round.
That to be said you don’t have to worry about your timetable BUT there are some months of the year that are favorable to climb because of weather conditions.
These months are usually the driest months, as climbing by rain and by snow can make your experience more exhausting and decrease success rates to summit.
As Tanzania is located close to the equator there is no summer and winter as in other parts of the world but there are rainy and dry seasons that change the amount of rainfall and temperatures. YES it is Africa and YES it does get very cold up on the mountain!
On your arrival day you will arrive in Moshi town where temperatures can easily reach 30 °C (86 °F). From here you will start to ascend everyday between 800m to 1000m.
You will basically cross an entire climate zone per day until you reach the summit (read: Kilimanjaro’s Climate Zones).
Especially summit night is a challenge as temperatures can drop down to -25 degrees Celcius (-13 °F).
That doesn’t mean that you won’t be able to climb during rain season, but the challenge is higher as hiking through rain and snow is more exhausting and slower than average.
The driest and warmest months:
January, February, September
Beginning of March, late June, July, August and October are also good months.
The coldest and raniest month:
April, May, early June, November, December