This is an old wives tale and not scientifically correct.
Water is liquid that is known to freeze at 0° C.
The boiling point of water is also 100° C.
If the farmer sprays the cherries on the tree with water, it suggests that they will freeze faster because water has high freezing point compared to that of the cherry.
This will not in any way protect the cherries on the tree.
To prevent the cherries from freezing, he should spray them with something that has lower freezing point.
