What is "thunder clouds"

Usage examples of "thunder clouds".

Strange to say (the result perhaps of the concussion of air occasioned by the blowing up of the city) huge, white thunder clouds lifted themselves up from the southern horizon, and gathered over-head.

He plunged into an outcropping of dark mist and dove into a knot of thunder clouds, hoping to lose himself in them.

There were mountains of cumulus thunder clouds standing tall over the distant sea, and the sun came up behind them so that they glowed with red and roses, wine and deep purples, each cloud etched in outline by brilliant red-gold and shot through with shafts of light.

And the deeper they went, the more obvious it became they would find no night men cat-treading shadow while strange tents plumed like thunder clouds.