Would cold water put out a fire faster than hot water?
One of the main ways water puts out a fire is by cooling the burning material to below the temperature at which it burns, so it would seem a good assumption that cold water would work better at extinguishing fire.
Cold Water... Brr
Technically cold water will douse a fire faster than hot water, but of course it's not that simple.
Remember, water takes heat from the fire, it cools it. The main way it takes heat from the fire is by becoming steam. When the water hits the fire and turns to steam it absorbs a lot of heat, making the burning material too cool to burn.
Although it is true that technically cold water will put out a fire faster than hot water, most of the cooling effect comes from changing the water into steam, not from raising the temperature of the water. In fact there's less than a 1% advantage in using cold water.