The herds in August are up in the north, crossing the Mara River between Kogatende and the Lamai Wedge. This is the peak time to see the river crossings because even if the wildebeest are late, they will have reached the Kogatende area by this time.
You would be very unlucky for the wildebeest not to be surrounding the Mara River if you decide to go in August. On the flip side, you would also be lucky to see a crossing, as not everyone does - no matter how many hours are spent waiting with a herd by the river banks, they may simply not decide to cross over for hours!
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