Tomato Frost :(

This week it snowed. It didn't really stick, but that night the temperature dipped down to about 29. That, coupled with the lack of sun for a few days allowed the cold frame to get rather cold. The min/max thermometer read 33 as a minimum temperature even with the cellar window cracked open that night. If you click on the photo and make it larger and look in the lower right you'll see that most of the tomatoes in the two tomato flats are dead. I knew it would be cold and I thought about taking the tomatoes inside, but I guess I wanted to see just how far I could push it. I had started them far too early anyway. It's not too late in the season so I've started some new ones. I do feel bad about killing the tomatoes that my neighbor gave me though. I walked over to peek into his cold frame this morning. He was not foolish enough to have put his tomatoes in there yet. My peppers and basil are still safe inside the house and are doing fine.
What I've learned is that if it's been a sunny day then the coldframe will retain the heat and weather slightly freezing temperatures staying 7 to 10 degrees warmer than outside. However if there have been a number of cold cloudy days in a row, the temperature in the frame at night will only be a few degrees warmer that outside. I'm suspecting that having the frame against the house is not helping much. In addition the chicken litter that is under the seedlings has stopped composting and is now providing no extra heat. For the rest of the spring, I'll keep track of how many days a tomato killing frost in the cold frame happens and if there are any frosts cold enough to the kill the cool weather crops. My idea is not to have a cold frame that requires a lot of supplemental heat, but if having heat tape or lights a few nights in a season will gain me weeks, I'll consider it. So the cold frame experiment continues...