Gradual Accumulation Edit Meaning

1.

It is when you can't put your windshield wipers on auto because the rain isn't coming down hard enough but still building up on your windshield. So you have to push the wiper lever manually for every wipe.

Gradual accumulation can happen when rain has slowed to become misty or after a rain storm and mist from other cars build up on your windshield.

See rain, wipers, drizzle