Tori, good advice from Rick about the cold frame... what are your nighttime lows now? The spinach, collards, kale, cabbage and lettuce may well be able to be outside now, once acclimated a bit. Generally when I put plants out in the garden, pretty much regardless of whether it's early in the season or even later on, I cover them with "floating row cover" (Reemay is one brand); it protects them from wind, from sunburn, and helps hold some moisture in the ground as well. A cold frame, on the other hand, really concentrates the heat... even in my unheated hoop house (a plastic-covered hoop frame) the temp got up to 79 today while the outside temp was only 40 -- on a fully sunny day, with lots of snow still on the ground here. I would definitely recommend leaving the cold frame very well ventilated unless the temp is going below freezing.
