thundercloud

a bank of thunderclouds;

一堆雷电；

thunderclouds that promise rain.

有雷就会有

thunderclouds of impending war.

迫在眉睫战争雷

that the electric charge would try to find the most direct route between thundercloud and ground.

因为我们认为它会在雷地面之间找到最直路线。