Ours came out for the first time last night too. Im in Michigan. We frequently re freeze after a thaw, I think they just tuck themselves back in where they overwintered.

They'll be fine. Frogs know how to survive, you'd be surprise.
You should here them singing in the ponds near my house, and I live in Zone 5 up here in Mass.!

Even after a late spring snow storm, they find a way to stay comfy while cold, and then come out at day to let get sun stoked with the much hotter sun now. They even have a way of hiding under brush, plastic and litter.

Besides, if they are singing now, the water temps have risen enough to get make them active, and they would just slow down if the water cooled off.

Mike