Afrinolla — Tanzania northern-circuit safaris: which | afrinolla.com

The short answer: match the month to the migration phase

The best time to visit Tanzania for the migration is whichever month matches the phase you want to watch — the herds move all year.

The Serengeti–Mara migration is a continuous loop, not a single event. About 1.3–1.5 million wildebeest and roughly 250,000 zebra travel around 800 km between Tanzania and Kenya, so the question 'when is best' only makes sense once a phase has been chosen.

Four phases anchor the calendar: calving on the Ndutu plains in late January–February, the push through the western corridor and the Grumeti crossings, the Mara River crossings from July to October, and dry-season game viewing from June to October.

Weather frames all four. The long rains fall in March–May and the short rains in November–December; the dry season between them brings 20–28 °C days and 8–14 °C nights on the plains.

• Late January–February — calving peak at Ndutu, up to 8,000 calves a day
• Mid-year, before July — the western corridor and the Grumeti crossings as the herds move north
• July–October — the Mara River crossing window
• June–October — dry-season game viewing, 20–28 °C by day

Late January to February: calving on the Ndutu plains

For sheer density of animals, the calving peak is the most concentrated fortnight of the migration year.

At the height of the season, around 8,000 wildebeest calves are born per day on the Ndutu plains. The herds gather on the southern grasslands and stay put while the calves find their feet.

Timing favours the traveller: the calving peak lands just ahead of the long rains of March–May, so the heaviest weather of the year arrives after the densest game concentrations.

Days still follow the park rhythm — gates open around 06:00–06:30, and the morning drive runs 3–4 hours from first light, which is when the plains are at their busiest.

July to October: the Mara River crossings

The crossings happen inside a four-month window — and on the river's timing, not the visitor's.

From July to October the herds bunch along the Mara River. A recognised crossing point is called a drift, and herds can wait several days at a drift before crossing at any moment within it.

That unpredictability is what planning must absorb: no operator, camp or guide can schedule a crossing for a specific hour, and a single afternoon at the river may show a massed crossing or massed hesitation.

The window sits inside the June–October dry season, so crossing-season travellers get 20–28 °C days and 8–14 °C nights — warm afternoons at the river, cold early mornings at the drift.