Explanation

Fire is extinguished by cooling the fuel and by smothering it, cutting off oxygen. Boiling water is already at the phase-change threshold, so it flashes into steam almost instantly, absorbing the large latent heat of vaporisation and generating roughly 1,700 litres of vapour per litre of water, which smothers the flames. Cold water must first be heated to boiling point before it can produce steam, so it acts more slowly, and ice is slower still. Hence boiling water extinguishes fire more quickly than cold water, hot water or ice.