The Serengeti is open year-round, and no time of year is bad — but timing determines what you see.
January to March is calving season on the southern plains. The wildebeest concentrate around Ndutu and the short-grass plains, and predator density is extraordinary. This is arguably the best time for predator sightings in the entire ecosystem. Weather is warm with some rain.
April and May are the long rains — some camps close, tracks can become impassable after heavy falls, and the park is much quieter. Prices drop significantly. If you have a 4WD and some flexibility, this is the least crowded season.
June brings the herds to the western corridor and the Grumeti River. Dry season begins, tracks firm up, and wildlife starts concentrating near water. The Grumeti crossings are less famous than the Mara but excellent.
July to October is the peak season: the dry season is fully established, the animals are concentrated around rivers and waterholes, and the Mara River crossings in the north draw the largest crowds. July and August can be extremely busy at the most popular crossing points, with many vehicles circling the same animals. Book camps well in advance.
November and December are short rains, much lighter than the long rains, and the herds are beginning to move back south. Wildlife is excellent and the park quieter than peak season. Landscape is vividly green after the rains.