Aestivation

Aestivation is a dormancy triggered by heat or dryness rather than cold — many frogs and toads dig down (and some form a protective cocoon) to wait out dry conditions.

It is the hot-and-dry counterpart to brumation. In the wild it helps animals survive drought; in captivity a healthy animal shouldn't need to aestivate if conditions are kept right, so a frog that buries and stays down is usually just resting, not in trouble — provided it holds weight.