Circadian rhythm:

For temperature studies, subjects must remain awake but calm and semi-reclined in near darkness while their rectal temperatures are taken continuously. Though variation is great among normal chronotypes, the average human adult's temperature reaches its minimum at about 05:00 (5 a.m.), about two hours before habitual wake time. Baehr et al. found that, in young adults, the daily body temperature minimum occurred at about 04:00 (4 a.m.) for morning types but at about 06:00 (6 a.m.) for evening types. This minimum occurred at approximately the middle of the eight hour sleep period for morning types, but closer to waking in evening types.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". How long before wake time is the lowest temperature reached?
two hours