Why can heavy rain reduce tire grip even when there's no standing water to cause hydroplaning?

Pick an answer

1. Tire grip only drops once water is deep enough to be called standing water, though that's not how hydroplaning actually works
2. Rain only affects grip once it accumulates into puddles
3. A thin film of water can still reduce friction between the tire tread and the road surface
4. Heavy rain actually improves grip by cooling the tires

Correct!

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