Значения для термина "heavy thundercloud" отсутствуют.
1 Outside a heavy thundercloud gathered and darkened the room.
2 Rilla scanned the sky also; she did not like its appearance; a heavy thundercloud was appearing in the northwest.
3 Warm air starts rising up into cooler climes and condenses to build dark, heavy thunderclouds .
4 It seemed as if a gloomy multitude of heavy thunderclouds had gathered over the still, blue arm of the sea.
5 It was a dark evening for the time of year; heavy thunderclouds were hanging low in the sky and obscuring the light.
6 It was then five o'clock, and the approach of darkness was accelerated by the heavy thunderclouds which were gathering over the northern mountains.
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