wanderingwalnutI used this at least once when the temperature dropped below 30°F/0°C, and paired it with a borrowed sleeping bag that was certainly not meant for cold weather (also worth noting that I placed my tent on a wood platform, not directly on the ground); I would rate my sleep as restless but sufficient, with some improvement after I wrapped some extra clothes around my feet. Not something sustainable, but it worked.
I am much more comfortable with this pad at 50°F/10°C or higher.