It is a well-known, documented human physiological phenomenon that a person's body temperature will lower during sleep and rise before waking. Whether the body temperature rise is considered a trigger to wake or the result of another process is unclear.
It is a significantly-less well-known that my normal daytime body temperature isn't the usual 98.6°, but rather, is the confusing 96.8° Every once in a while (say, like, once a month, you make the connection), my normal temperature rises to 97.1°, but it generally hovers below 97°. Anyone who has touched my hands or other extremities can attest to this generally always cold(er than normal) temperature.
Upon waking, however, tying both these facts together, is the newly documented fact that as I wake, my body temperature spikes. It usually goes over 100° and rarely goes to less than 99 and something degrees as I wake up. 99+° is pretty "pfft" in the grand scheme of body temperatures, until you recognize it is a 3+° bump. Not bad, not bad.
Normally, I am amused by the spike. I AM THE FURNACE in the morning. I've been like this all my life, so I consider it normal. The furnace turning on signals to me it is time to leave the bed in the morning.
I'm not actually likely to leave the bed, but I have the signal.
I want to say that the furnace triggering doesn't bother me, and it usually doesn't bother me.
It does, however, bug the crap out of me (no, not literally) when it triggers at 2:51 in the morning. No, jet-lagged body, it is NOT time to get up, it is NOT time to get out of bed, it is NOT time to start the day.
Which is all really amusing, except it really is the signal to wake up and get up. I have been struggling to fall back asleep these last four nights after waking at two something in the morning. At first, it was amusing, and I would read. Now it is becoming frustrating. When my bedtime is now 8:30pm so that I can go to sleep then wake at two something, read until five something, then sleep again until nine or ten in the morning, and this goes on for days, I fear it turning into a permanent sleep pattern. Sure, I'm reading a LOT these nights, which is great, but having only 12 hours of waking time to do life activities makes for a difficult set of days.