Boiling water challenge sends at least 8 people to hospital during polar vortex...

[ProfessorGAC]

13. Vapor/Liquid Equilibrium

At 210 degrees water exerts a vapor pressure above the liquid of nearly 0.84 atmospheres or around 13 psi
Under nearly all conditions, there is an equilibrium of liquid and vapor. That's true of essentially every liquid especially notable in things that liquid over a wide range of temperature
Different liquids (say ethylene glycol) has a different equilibrium curve than water but it's still the same concept
The water itself would do it too, but it requires more motive force to aerosolize liquid water.
The rapidly cooling gas condenses into microscopic droplets due to physics. No special other impetus is required.
The heat is transferring into the cold air so it is going somewhere. The water is giving up the heat to phase transition from vapor to liquid.
Think about it: do the exact same test with room temperature water.
The effect is dramatically reduced because the vapor pressure above the liquid is a 25th or so. That's so much less mass of water, that the cloud of ice crystals isn't anywhere close to as intense
That's the point of heating the water to around boiling.