torrential
Very heavy and intense, pouring down like a huge rainstorm.
Torrential describes rain falling in enormous, overwhelming amounts, like someone dumping giant buckets of water from the sky. When weather forecasters warn of torrential rain, they mean far more than a typical rainstorm: they're talking about sheets of water so heavy you can barely see through them, the kind that floods streets in minutes and makes driving dangerous.
Picture a waterfall crashing down a mountainside after snow melts in spring: that violent, unstoppable flow captures what torrential means. When rain falls torrentially, it doesn't just drizzle or sprinkle. It pours with an intensity that can overwhelm storm drains and turn sidewalks into rivers.
People sometimes use torrential metaphorically for other things that come in overwhelming quantities. A popular author might face a torrential flood of fan mail, or a student might endure a torrential stream of pop quizzes. In these cases, the word suggests the same feeling of being swamped by sheer volume, though no actual water is involved.