Extended low temps like this can stunt them.
Even lightweight garden fleece can help a little -- maybe 2-3 degrees -- heavier garden quilt will keep temps about 5 degrees above. BUT you need to take the covers off as soon as the direct sun is on them in the morning and heats up above ... I'd say 57Â°F if you have peppers and squash in there, 52Â°F if just tomatoes.
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