Does artificial heat (shower/tea) affect diurnal rhythms in humans?
Yes, the human body has thermoreceptors that "sense" the current temperature, but these merely help with regulation--you know, shivering to raise internal body temperature and sweating to cool via evaporation. The hypothalamus is primarily responsible for making sure that the circadian rhythm itinerary is adhered to reasonably well. So no, if the thermoreceptors detect that the body temperature is 97 deg F but it's 5 pm, the body will not "get confused" and decide that it is actually 4 am because a human body is about 97 deg F at 4 am.