You can get by with using just about any sleeping pad in the summer, spring or fall, but in the winter, 4 season sleeping pads are a definite investment that you want to make, if you plan on being comfortable while sleeping at night.

The great innovation that 4 season sleeping pads have, that other, 3 season sleeping pads do not, is that they use some sort of insulating material, which then absorbs your body heat and reflects it back at you. The net effect is that you do not lose that body heat, but are instead warmed by it.

When trying to find a warm sleeping pad what you want to pay close attention to the is R-value of the pad. This is a measurement borrowed from the construction industry, and basically, a high r-value, of 8 or 9 means that your sleeping pad will reflect quite a lot of body heat.