According to the manufacturers data the indpendent test performed by Leeds University gives the Blizzard Bag a TOG rating of around 8. This would be equivalent to a summer bag i.e a 0.8Kg good down mummy bag. According to the EN13537 specification this would equate to a lower limit of comfort of around +3 degrees Celcius and an extreme temperature rating of around -5 C to -9 C. (serious risk of death through hypothermia)