Some states do require, so it would be worth it for you to contact a local employment attorney to find out. My smaller clients do not pay at all.
Larger ones do pay for one or two weeks.
If you decide to pay, make sure you put a limit on it. Similarly, no federal law on snow days. I'm pretty sure there are no state laws on this, but again it would be good to ask a local lawyer. For example, in California they have to be paid at least 2 hours. I would pay for my employee's time during jury duty.