A cold frame is a great tool for any climate. A gardener can use it to get a jump start on the growing season or to extend the growing season as winter approaches. I was lucky enough to be gifted one this past Christmas.
What I have is actually called an “elevated patio grow house” and is sold by Gardener’s Supply. However, a cold frame is really just any structure that works as a miniature greenhouse. It catches the sun’s heat through transparent glass (or in this case plastic) and keeps the seedlings and dirt warm. The temperature at which seeds germinate is really all over the map, but a good rule of thumb seems to be that most will germinate when the dirt is between 60 and 75 degrees.
I’ve had great luck with mine so far this spring (wait…it isn’t spring yet, is it? Oh southwest…. you mess with my mind) winter.
Cold frames can be easily constructed at home, using wood and an old window (if you are one of those people that has old windows just sitting around). Here is a picture from This Old House of one made this way.