What happens when supersaturated solution cools down?
if cooled carefully the supersaturated solution will stay liquid unless disturbed or seeded with a seed crystal.
An excellent experiment is to heat sodium thiosulfate in a water bath. The solid crystals will dissolve into the water in the hydrated crystals forming a supersaturated solution.
If the sodium thiosulfate solution is cooled slowly the supersaturated solution will remain liquid. Placing a small crystal in the supersaturated solution will cause the liquid to turn solid.
( Note the "freezing " of the supersaturated solution is an exothermic reaction and releases a significant amount of heat as it turns solid. watching the reaction under a microscope as the crystals form is fascinating.
The moisture in the air can also be a supersaturated solution. Dust silver nitrate or a sudden change in temperature can cause the supersaturated solution to loss all of the extra moisture and rain.