"The mountain is covered in snow" 或者 "There is snow on the mountain" 可以用来描述山上都是积雪的情况。

这两句话的来源是英语中常用的表达方式。"The mountain is covered in snow" 中的 "covered" 是动词，意思是"覆盖"，"in snow" 是介词短语，意思是"用雪"。"There is snow on the mountain" 中的 "there is" 是助动词，意思是"有"，"on the mountain" 是介词短语，意思是"在山上"。

下面是一些英文例句以及中文翻译：

The mountain is blanketed in snow. (山上被雪覆盖了。)
The snow on the mountain is several feet deep. (山上的积雪有几英尺深。)
The slopes of the mountain are covered in a thick layer of snow. (山的斜坡被厚厚的一层雪覆盖着。)

希望这些信息能帮到你！