When the rain is coming down hard, we often use the phrase "pouring down on" to describe it. However, there are several other synonyms that you can use to add variety to your writing. You can say that the rain is pelting, drenching, lashing, or beating down on you. Alternatively, you can use the word "torrential" to describe heavy rain that comes down in a sudden and intense manner. You could also use phrases like "sheets of rain" or "buckets of rain" to give your writing a more descriptive flair. Using various synonyms for "pouring down on" can make your writing more interesting and engaging for readers.