If you want to extend your vegetable season consider a cold frame. Cold frames are mini-greenhouses that cover part of your garden bed, keeping the soil and air warmer and fighting off frost. They can be as simple as an A-frame using storm windows and fabricated end caps. Keep in mind that on sunny days they can overheat quickly, so build them so that they can be easily opened and closed. If you maintain a uniform bed size you can leapfrog the cold frame sequentially in the spring, first to jump start salad greens, then to get a head start on tomatoes and peppers.
