For the mechanism and evidence behind this sequence, see Sleep Thermoregulation in Understand.
The protocol
- T−120Drop the thermostat. Rooms lose heat slowly; set it two hours out so it is at 18 °C when you lie down, not two hours later.
- T−90Hot bath or shower, 40–42 °C, at least 10 min. The rebound vasodilation — not the heat itself — is the mechanism.
- T−30Socks on if your feet run cold. This is the single cheapest intervention on the page and the one most people refuse to try.
- T−0Breathable bedding, hands and face uncovered. Duvet tog matters more than the thermostat if the duvet traps the heat you just released.
- T+240Allow a small rise toward morning. A flat setpoint all night is not what the circadian curve asks for.
If your room cannot hold 18 °C on its own — a partner, a climate, a shared thermostat — see the Eight Sleep Pod 4 review, or start with a logging thermometer to confirm your real number first.