Today it rained in Houston, but I had to get about and I discovered something I didn’t know about my car. When the rain started as a sprinkle, I put the wipers on intermittent.
Suddenly the rain picked up, and so did the wipers, to regular speed. When it became intense, the wipers ramped up to match. Then, when I pulled up to a covered ATM, they stopped.
When I pulled out again, into a light drizzle, they started up on intermittent again.
Knowing what kind of car you’re driving would help. Ones I’ve made were two closely spaced wires, but I bet most car rain detectors work like this. Check your rear-view mirror for wires.