Fluffy altocumulus undulatus clouds stain the sky red above a row of trees. These mid-level clouds, which form. above 6,500 feet (2,000 meters), often herald an approaching storm.是什么意思_Fluffy altocumulus undulatus clouds stain the sky red above a row of trees. These mid-level clouds, which form. above 6,500 feet (2,000 meters), often herald an approaching storm.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句