Dave,
Russ here from NH. Even in the summer we often find ourselves in your perdicament. We'll be glasing all day and then the mercury goes south.
We use a varity of solutions that have already been mentioned.

One of our other solutions is a curing tent. Using scrap 2X4's rope duct tape clamps etc. Then we put big tarps, army blankets old bedspreads etc on the frame. We put the boat inside the tent on top of a strong back. Under the strong back we evenly space a few tungston work lamps or some a 100 watt study lamps.

Our quick build curing tents look like a homeless person's abode, or a sweat lodge on steroids, and at night with the lights glowing throught the tarps and fabric, it looks like a UFO that landed in the back yard. Which is all part of the fun. (Good to keep the neighbors guessing)

Our curing tent has kept the dew off, kept the heat up and has worked for us even in nights that drop to 30F.

In fact, we have found its important to leave a vent hole on the top so it doesn't get too hot.

Hope this helps

!RUSS