I would wait until this next cold front has passed. It's supposed to get into the single digits. Probably too cold for seedlings unless they are covered with snow before the deep freeze kicks in.

gjcore has great advice.

Also,it has been helpful to me to observe what nature is doing plus using a thermometer to track the soil temp. So in your yard it would be great to see when the lilac is leafing plus see 9 am soil temps at 40ú to think about putting in sets. Even then keep the forecast in mind.

I agree that it is good to have indicator plants: lilac, forsythia, currant. Some indicator plants don't mind cold, others do.