I posted this under tomato horn worms, but that was not what I intended. I live in a mountainous zone 5 where frost free days can go between 80 and 120-130. It is problematic to get tomatos and melons some years, both of which are favorites. I grow tomatoes against a south facing wall, inside a 5 gallon bucket with the botton cut out and a couple gallon jugs of water down along the stem. This helps immensely, but I wondered if I might get some things earlier if I had a protective area to start them earlier.
If frost threatens it is easy to throw row cover over the pails or what ever you use to contain heat around the bottom of the tomato plant. I leave the water jugs there all season as it helps keep the night time temperatures up and helps fruit to set better
The hoop house is still under construction so success will not be known for a while.