Usage patterns
土砂降りになるto turn into a downpour
It suddenly turned into a downpour in the afternoon.
土砂降りの中を〈動詞〉to do something while walking/driving through a downpour
I walked home through the downpour.
土砂降りに降られるto get caught in a downpour
I got caught in a downpour on the way home and got soaked.
土砂降りが続くfor the downpour to continue
The downpour has continued for over an hour.