If you can say what kind of seedlings and how cold it actually gets out there it would be easier for people to respond intelligently. If it is only petunias, I wouldnt expose them to anything less than 45 degrees while they are young.

You might try to rig up something with an old electric blanket for the least cold tolerant plants.

I don't really know if they are seedlings any longer. These petunias are just over 6 weeks old and average 2.5 inches tall by 2-3 inches across. They are in 4 inch pots now. Just petunias. It snowed 4 days last week and dipped down into the 20's. From now on, I don't think it would any colder than 35 degrees on the porch.

I have some petunias that I spring sowed outside and they are under a thin clear plastic. Mine have just sprouted and dont have true leaves yet. Our temps here dropped to 29 tuesday night. All I did was put an additional tarp over them and they are fine now. If your porch doesnt go below 35 I think they would be ok. If in doubt cover them with sheets.

Thanks all. Last night it got down into the low 50's and all is fine. Tonight they say a low of 29 degrees, so I'll be bringing the plants inside. I may leave one pot out to experiment.