What is the coldest night germinated seeds can withstand?? (live in IN)

I live in Northwest Indiana. I Have some seeds I'd like to germinate and then plant, but I am fearful that it gets too cold at night this time of year. I'm not really in a situation where I can bring them inside either.

This time of year it's maybe mid to upper 60's on average during the day, sometimes into the low 70's. What i'm concerned about however is mostly the big drop in temp at night. It gets down to the mid 50's right now, which from everything I've read is too cold for healthy plants. So basically looking for advice on when a good time to plant would be(or maybe I'm mistaken and I can plant now)? Once the coldest point at night is around 60 or so am I good or does it need to be warmer at night even?

-Thanks!

It got down to 33 and 36 on two nights in a row, I had some sprouts hangin in it till three a.m. the first and four the second and they are just fine, dnt know about seeds under the ground though. when i say until the posted time i brought them inside till ten a.m. Hope I helped.