Where have you camped? Has the ground always been warm?
Not always.....
A quick trip down memory lane; Dog Canyon New Mexico, Christmastime maybe five years ago, temperatures in the teens me and the dog brung three Chinese exchange students who "had never seen the stars" (air pollution) camping.
They occupied my dome tent upon mats and buried under blankets and sleeping bags. Me and the dog did alright on a groundsheet under wool blankets but this was one of the few occasions she chose to sleep UNDER the blankets
But points well taken re:temperature issues.
Mike