One season sleeping bags are the most lightweight and travel friendly but are at the lowest end of the temperature scale, recommend for use in warm destinations or indoors where they will keep warm around 10-15 degrees. Two season sleeping bags are slightly bulkier than the one season sleeping bags, due to the extra insulation, but will keep you warm to around 5 degrees. Three season sleeping bags are best for use in Spring and Autumn can also be used for Summer time campers who feel the cold a lot as they will keep you warm down to around 0 degrees. Four season sleeping bags are ideal for all year round campers and will keep you warm down to around -10 degrees. Not generally known on the market, five season sleeping bags do also exist. These have been designed for extreme weathers and conditions and will keep you warm down to around -40 degrees. Please always check the comfort temperatures of the sleeping bag you are choosing, as these are just guidelines.