The few warmer (60 degrees and higher) days, that we seem to have every once in a while, is a good time to start hardening off your vegetable plants.
Hardening is needed to acclimate your plants to the great outdoors after they have been cuddled and nurtured in a perfect indoor environment. It gets them used to rain, wind and stronger sunrays. Think about what happens to your skin when you go outside and start working in your garden after having been inside all winter. Same thing happens to your plants.
Start out gradually with a short amount of time and then slowly work up to a full day. If you are going to plant your plants outside the latter part of May, then you have until then.
I have had my plants out already several times. The first time it was gray and a little warm. They were outside as I repotted them and they got a chance to experience a light breeze in a protected spot next to my house. Today the sun is out so they will only be going out for an hour.
Once you are eventually able to leave them out for the day, don't forget them at night. Last year I forgot about my cucumbers and then we had that sub-freezing weather that destroyed most of the apple blossoms in Allen County. My cucumber plants looked rather dead the next morning. Too much hardening too soon can kill.