Sleeping tents are passively warmed by the sun. Temperatures will vary depending on the time of day, weather and the type of the tent.
Larger “clam” tents can warm to between 60F and 68F (15C and 20C) during the daytime, a comfortable temperature when wearing thermal and fleece layers. Temperatures are cooler on cloudy, stormy days and and may drop to near freezing at 'night', when the sun is less intense. You will sleep snugly in your polar-rated sleeping bag whatever the temperature.
Small, mountain tents used in field camps can be 80F (25C) on a sunny, windless day - almost too warm to be inside! Again, inside temperatures are cooler on cloudy, stormy days, when the ambient air temperature is very low, or when the sun drops behind a mountain ridge (e.g. at Mount Vinson).
