Inevitably, the weather will be the biggest factor you need to take into account when deciding when you want to climb Kilimanjaro. Essentially, being close to the equator, the temperature on Kilimanjaro varies little throughout the year even though it does vary hugely between day and night and as you climb to higher altitudes.
What does change during the year is expected rainfall. Kilimanjaro has a long rainy season in April and May when monsoon-like rainfall can be expected in short storms every day and a short rainy season in mid-November to December when it is generally less stormy. Outside of these periods you can expect most days on Kilimanjaro to be warm and dry.
Of course most people want to climb when it is expected to be dry so choosing when to climb then becomes a trade off between when it is likely to be dry but busy or wetter but quiet. If you can cope with some rain you can have the mountain pretty much to yourself in April and May!
Besides the weather there are two other things you might want to think about in deciding when is the best time to climb Kilimanjaro. First is flight prices: these vary a lot during the year and tend to peak during the European summer holiday periods. Prices vary as much as 50% so this has a big effect on the overall cost.
Second is the timing of the full moon. Some people love to climb Kilimanjaro under the full moon as it gives more light for the summit night climb. Some prefer to avoid this date as the stars are really spectacular when there is no moon. It's down to you but we can let you know when the full moon will be in the month you are looking to climb. And as we once had to explain to a teacher who enquired - there is generally just one full moon a month!