The best time to visit Axum is between October and March, when temperatures are mild (15–28°C) and rainfall is low. The main rainy season runs July through September, when afternoon downpours are common and the roads into town can become difficult.
The most spectacular time to be in Axum is during Timkat (Ethiopian Epiphany), which falls in late January (usually 19–20 January by the Gregorian calendar). This is Ethiopia's most visually dramatic religious festival: priests carry replicas of the Ark of the Covenant through the streets in a torchlit procession the evening before, and the following day involves baptism ceremonies at Mai Shum reservoir and open-air liturgy. The scale and intensity of the celebration at Axum — the holiest site in Ethiopian Orthodoxy — exceeds what you will see anywhere else in the country.
Meskel (Finding of the True Cross, late September) is another major festival celebrated with bonfires and ceremony throughout Ethiopia, including in Axum.