All the maps and tourist guides recommend that you NOT try to descend from
the rim to the river and climb back in the same day. The height difference
is not that big (1500m - so less than some demanding Romanian trails, which
can be hiked out-and-return in a single day without problems) but during
the summer the temperatures inside the canyon reach 50 degrees Celsius in
the shade (!) and the reversal of the effort - first go down, then go up -
can terminate you. So if you managed to get to the river level but you're
finished by the heat, jump in the water! When I was there, at the end of
September, the canyon temperature was 32 degrees Celsius in the shade.
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