Temps too cold, any ideas?

Howdy,

Starting on my 2nd grow, about 1.5 months in, and the temps in my area (WA) are getting colder then I'd like the plants to be in, the range is generally about 58-84 for the flower section. I don't really have room for a heater and already have insulation under the cab and solid materials surrounding, but its still in a garage. What have other people used to keep the temps up during the night? I'am going to put their light period during the night, and see how that does in the overall swing of temps....

thanks for the comments.....

heating pad its flat it will keep the roots warm for the most part

I have the same issue. I'm growing in a crawl space in my garage, and it can get pretty cool at night. A heating pad is an interesting idea... just put it under the pots?