At 18°C, tonight sits right in the zone where sleep research says most adults sleep best. Your body can regulate its temperature naturally without any intervention.

The dew point — 18°C — is the real problem tonight. High dew point means your sweat can't evaporate, which is your body's primary cooling mechanism. This is why humid heat feels worse than dry heat at the same temperature, and why a fan helps more than you'd expect.

The air barely cools overnight — just -0.3°C between bedtime and 4am. Your body's circadian rhythm expects a temperature dip during the night. When the environment doesn't provide one, sleep becomes lighter and more fragmented, even if you don't fully wake.