RickCorey_WA wrote: I think it depends on how effective the cold frame is. For example, if you have plenty of sun and no wind, and the cold frame has no leaks and good insulation, it should be like a safe, warm greenhouse that will keep plants warm enough all night. Just don't cook 'em!
But if the cold frame has leaks (like mine) or is in the shade (like mine), or you have a lot of wind any ANY leaks, they might not like the chills at night.
Do you have any recording thermometer? I found a cheap battery-powered one that remembers high and low temps. That would tell you how cold (or hot) it got while you weren't watching.
My plan was to not let my seedlings get too accustomed to "warm" for a long time. I can almost expect some late, unexpected cold snap. Or rather, there are always long warm spells that occur BEFORE spring is "really" here. I'm afraid that my cold frame might protect them too much in early warm spells, but soften them too much to survive a last chill.
I haven't actually used a successful cold frame yet, so I really hope that someone more experienced will chime in!