Answer: You can set out seedlings of cool-weather crops two to three weeks before your last frost date, which is probably around the first week of April in your region. They can take cool weather but not repeated hard frosts. And you need to acclimate them over the course of a week or two before transplanting, to harden them off so they can get used to the harsher outdoor conditions. Even so, I'd plan to cover them if a hard frost is predicted, because tender plants can be stunted. You might be able to rig up some type of cold frame for the plants, so you could set them out a little sooner. I've used some old windows laid on top of some hay bales, then set the plants underneath. You just need to watch so they don't overheat, and cover the windows with a blanket if very cold weather is predicted.
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