In early July, the herds of wildebeests and zebras arrive in small groups to the Maasai Mara from the plains of Serengeti, the Northernmost part of the Serengeti, where the river Mara flows on the border with Kenya and the Maasai Mara Reserve.
It’s quite difficult, however, to time the Great Migration from the Serengeti and when the herbivorous start arriving in the Maasai area, as the animals follow the rain and their journey is dictated primarily by their response to the weather.
Sometimes it may happen that they arrive to the Serengeti Mara in late June or have just started their Northward journey in mid-August.
In this part of the route, the herds follow two possible paths:  the first is the Northern Corridor, where the wildebeests pass to the North of Seronera and immediately head North; while those taking the second path  go through the Seronera valley again and then go straight to the Lobo area in the North and to the Serengeti Mara.
When the herds arrive at the river Mara, they gather on the bank waiting for as long as possible, holding on until they can no longer wait.
It often happens that tens of thousands of animals on the river bank move in multiple directions until someone starts the crossing.
This is one of the most difficult and critical points of the entire migration: the river Mara is considerably larger than the river Grumeti with its sandy banks and often with abundant water due to heavy, raging rainfalls.
And to make things worse, like at the river Grumeti, big crocodiles patiently await for celebrating a big party. 
Once here, the herds are clearly reluctant to cross the river and it often takes days searching for the right place where to jump into the water and reach the other side.
When the first wildebeests begin to cross all the others follow, forming columns of animals which, not without difficulty, walk and jump in deep waters trying to avoid rocks and other hazards, like eddies and points where vortices are stronger.
The danger is not only being swallowed by the crocodiles but also risking to get injured with a broken paw or being dragged away by the current and being drown.
What many do not know is that during their transit in this area, the herds cross the river Mara several times, partly because the river has several bends and hence the animals, heading Northwards, intersect it along their journey, and partly because they continue to move between Kenya and Tanzania in constant search of fresh pastures  and are inevitably forced to overcome their fear and cross the river anyway. 

Where is possible to spot the herds of Great Migration in July

Lobo: this extremely scenic area situated to the North-East of the park is dotted with numerous rocky outcrops, known as kopjes, the favourite locations where lions use to stand for spotting prey.
Many animal species live here all year round, such as elephants, buffalos, lions and leopards.
Serengeti Mara and the Lamai Triangle: like at the Maasai Mara, this far-reaching area witnesses the most scenic crossings of migration.
The land is very similar to the Maasai Mara, extensive green plains, undulating at some places, with shrubs and trees, that are much loved by leopards. 
The river Mara is inhabited by the big Nile crocodiles, while the mainland is populated by lions, giraffes, various species of antelopes, leopards, cheetahs and hyenas.
Elephants can also be spotted here, though less in number.
Maasai Mara: in July, the first herds coming from the Serengeti will spend 2-3 months here and then will resume their journey Southwards guided by the rains.
With its plains and hills, the Maasai Mara Reserve offers the wildebeests extensive grassy pastures, but the area is also covered by shrub and tree savannah.
A high concentration of animals can be found here, such as lions, leopards, elephants, giraffes, hyenas, antelopes and gazelles.