There is no way to accurately predict the timing of the migration as it depends on weather cycles. However, experience tells us that migration usually begins in the Serengeti National Park after calving season in February to March. By April into May, the food supply is exhausted, and herds begin to migrate towards the grassier plains. These lie to the west and north of the Serengeti. By June, the massive herds gather at the south side of the Grumeti River before fording its crocodile-infested channels and pools.

The survivors then continue north into Kenya, spreading across the plains before crossing the fast-flowing Mara River. There are often great scenes of panic and confusion at this crossing as strong currents sweep away exhausted animals, and hungry crocodiles lie in wait for others. Cows can easily become separated from calves during massive stampedes over banks into the water.

The plains of the Masai Mara National Reserve are usually covered in wildebeest and zebra from September through November. The cycle begins again after the short rains of November, when the herds head south to the southern Serengeti and Ngorongoro Conservation Area.