They had the same law while I was living in NY. I still go by it after living back in CA for over a year. Though I didn't know it was now a law here too.

 

I already turn my lights on if it's raining that hard. It's just common sense, driving in downpour is worse than driving at dusk.

Oh, and...

 

"hear"

 

Given what goal they are trying to achieve, I think this is the best wording.
It's not that "if you have your wipers on", it's "when conditions require" it.

Now, determining what "conditions require" wipers to be on may be something that
is difficult to define. I'm sure the judge will probably just take the officers word
that the conditions required it...