If you have the same LaFuma 40ºF bag that I have, I'm not sure it would be comfortable even to 40ºF. I have two 40ºF down bags, one by LaFuma and one by Mtn. Hardwear. The Mtn. Hardwear bag is considerably more lofty... even with fluffing in the dryer I'm not impressed by the LaFuma's loft, and seriously doubt I'd use it outdoors by itself below 60ºF. I have used my Mtn. Hardware in a hammock, with a light jacket, down to about 35ºF and been warm as toast. My son took the Mtn Hardwear bag for his bed (his reminder of 'mom' since he doesn't live with me 5 days a week now), and the LaFuma lives on my couch. I might use it as a liner for my 32ºF synthetic bag, but that's about it.

MNS