If you use a heating pad, place a towel or two between the plants (or clones, or seeds) and the pad, or even better...raise the plants off the floor, and keep an air-space between the pad and the pots. Monitor for a couple hours to verify it doesn't get too hot. The warmer temps will evaporate the moisture quicker, too. :thumbsup:

Raising them off of the cold floors helps. If getting too cold at night, you can reverse the lighting schedule, so lights are on all night during the coldest hours.