Ethiopia’s annual Christian celebration, Timkat, takes place around the middle of January and, although crowded with tourists and known for large gatherings, this is an amazing event to witness first-hand especially with the relatively mild temperatures.
If you're planning on visiting Ethiopia any time over their winter period, which runs until February, you need to be aware that it can get cold in the highlands, especially at night.
The Simien Mountains and northern areas, around towns like Lalibela, start to get a little warmer from March and trekkers will find ideal conditions with the occasional shower never too problematic.
Regions around the Omo Valley in the southwest of Ethiopia are the first to experience the shorter belg rains in April with the wetter weather moving eastwards into Bale Mountains National Park and the Rift Valley Lakes during May and June.
As the heavier and more permanent rains of the kiremt season really start to kick in around Simiens and Bale in July and August it's probably advisable to give them a miss around this time of year and opt for Omo and Mago national parks instead.
Ethiopia’s rainy season can stretch into September although around October you'll find the best time of year to visit the central highlands and northern circuit with lush green landscapes featuring carpets of yellow meskel flowers as well as easier traveling conditions.
One of the best times to visit the South Omo Valley and the Danakil Depression on the Eritrean border are the months of November and December as temperatures are lower with little or no rainfall.
In general, avoid the rainy season from June to August and bear in mind lower temperatures the higher the altitude and hotter conditions the lower you go and the further east you travel.