Short answer
The wildebeest reach Kenya's Masai Mara between late July and October, with the Mara River crossings concentrated in August and September. Roughly 1.3 million wildebeest and 200,000 zebra move north from the Serengeti. Calving season, a separate spectacle, happens in Tanzania's southern Serengeti in February.
The migration is a continuous year-round circuit, not an event, so the question is really where the herds are in a given month. They spend December to March on the southern Serengeti short-grass plains, move northwest through the Grumeti in May and June, cross into the Mara from late July, and return south from late October as the short rains begin.
River crossings cannot be scheduled. Herds mass at the Mara River bank for hours or days before one animal moves, and a three-night stay in August gives a reasonable but not certain chance of witnessing one. Guides position at Lookout Hill and the Talek and Sand River crossing points from first light.
August and September in the Mara are also peak season, with camp rates 60 to 90% above April and conservancy fees at their highest. Anyone prioritising general game viewing over the crossings gets better value in January to March, when the Mara is green, quiet and full of resident predators.
| Months | Location | What you see |
|---|---|---|
| Jan–Mar | Southern Serengeti, Ndutu | Calving — around 400,000 births in three weeks, heavy predator activity |
| Apr–May | Central Serengeti, Moru | Long rains, herds moving northwest, lowest rates of the year |
| Jun–Jul | Western corridor, Grumeti | Grumeti River crossings, crocodile activity |
| Late Jul–Sep | Masai Mara, Kenya | Mara River crossings, the classic image, peak pricing |
| Oct | Northern Mara and Loita | Herds beginning to turn south, crowds thinning |
| Nov–Dec | Eastern Serengeti | Short rains, dispersal south, good value green season |