Frog too early...Help

I had a serious pond issue that required me to move my fish indoors
during this past weekend's warm Chicago weather. A leaking liner left
me with about 12 of water and lots of fish and muck...somehow they
survived the winter, but I was afraid cats, raccoons, etc would get
down in there.

Anyway, in the process, a big frog shows up and starts swimming around
(coming out of hibernation?). Well, I brought the frog inside and now
we're expecting more really cold weather.

What can I do for this large, (Leopard?/ Green?) frog? Will it die if
I put him back out in the woods? Will he figure out how to survive?
We've still got some cold weather and I know there are no insects
outside. I bought him some crickets but the frog seems pretty
uninterested.

I have no experience in this realm and don't really want a pet frog,
but also don't want him to die...

Kevin