Adam Clarke on Job 24:8

They are wet with the showers of the mountains - Mr. Good thinks that torrents, not showers, is the proper translation of the original זרם zerem; but I think showers of the mountain strictly proper. I have seen many of these in mountainous countries, where the tails of water-spouts have been intercepted and broken, and the outpouring of them would be incredible to those who have never witnessed similar phenomena. The rain fell in torrents, and produced torrents on the land, carrying away earth and stones and every thing before them, scooping out great gullies in the sides of the mountains. Mountain torrents are not produced but by such extraordinary outpourings of rain, formed either by water-spouts, or by vast masses of clouds intercepted and broken to pieces by the mountain tops.

And embrace the rock for want of a shelter - In such cases as that related above, the firm rock is the only shelter which can be found, or safely trusted.