You can visit Kilimanjaro at any time of the year despite the fact that weather is erratic. During November to March the path remains slippery and may be the forest path leading to the summits are snowy. Western Breach will be covered by snow. Located near the tropics, it has no particular winter or summer months. The seasons are differentiated by the dry and wet (rainy) spells.
However the best time for trekking and climbing Kilimanjaro mountain is during the dry season between June to October and also from December to February and early March.