Even with all the vents open, it was 105°F in the greenhouse on Saturday, so I covered the flat-plate collector, shut down the pumps, and put up shade cloths. Then we got a late-season snowfall.
Nights were still around 50°F inside, so no damage. I've got tomato and bell pepper seedlings for the local community garden/food program, and they look really good. I start them on heat mats under covers, then use grow-lights when they are a couple inches high, so they don't get leggy.
