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Why a warm bath makes you sleepier — the cooling paradox
💡 Falling asleep depends on your core temperature dropping, so warming your skin — via a bath or a cool room — paradoxically helps by letting your body shed heat.
It feels backwards, but to fall asleep your body needs to cool down, not warm up. As bedtime approaches, your core body temperature naturally drops by about 1°C, and this dip is one of the signals that tells your brain it's time to sleep. The temperature fall works hand-in-hand with melatonin, the hormone released as darkness sets in.
Here's the paradox: taking a warm bath or shower an hour or two before bed actually speeds up this cooling. The warmth pulls blood toward your skin and hands and feet, and when you get out, that widened blood flow radiates heat away from your core — dropping your internal temperature faster than if you'd done nothing. Researchers call this vasodilation, and it's why warm feet can mean a cooler core.
The same principle explains why a cool, dark bedroom (around 18°C / 65°F for many people) helps you fall asleep and stay asleep. A room that's too warm fights against your body's natural temperature drop and fragments your rest.