It's very light but I was fine with this and a fleece down to the upper 20's. I don't think you can go much lower than that. I also bought the 800 fill version and couldn't tell much difference except the sleeves were much, much longer. I love these.
Sorry there is not a temperature rating. Most manufacturers do not have temperature ratings for their garments or footwear due to the number of factors that affect how warm a garment may keep you.