This is really surprising. All the studies I have read say precisely the opposite. The theory goes that because, in the environment in which our minds evolved, the temperature would ALWAYS drop at night, this is one of several signals your body responds to to prepare for sleep. Others include lower availability of food and darkness.
It goes against my experience as well. Years ago someone on HN equated an ice bath to elephant tranquilizer. So I tried it and can confirm it had a similar effect on me. In addition, I grew up in a cold climate. Being cold and absorbing my reflected body heat under the blankets made it so much easier to sleep. In contrast, hot humid nights were impossible.
