Many sleeping bags can be identified through their seasonal rating, this rating indicates that the bag is suitable for certain seasons of the year. For example, the Vango Nitestar 250 is a two-three season rated product, ideal for Spring, Summer and occassional Autumn usage. Here, we have a range of 1-2 season, 2-3 season and 3-4 season rated bags, which can provide adequate warmth for whichever season you choose to camp in. If its the height of summer, and the temperatures are high, then you will definitely require a 1 season bag, and so forth. It is always an excellent idea to check the variable sleeping temperature rating of the bag, to make sure it is fit for your purpose.