> hydroplaning when there is over 1" of standing water on the road because it's coming down faster than gravity can drain it away?

I'd say that's pretty calculable, and has a solution, slow down to a speed that the tires can shed water.

Perhaps most telling about your qualification is the misplaced risk; the light precipitation with a little oil slick is likely more dangerous, mostly because you don't slow down for it.

Anecdotally, an even harder problem is when water exceeds 4", negotiating with traffic so you won't float away or get water in your intake.