What makes the fields white with mist at night in the hot weather?

The hotter the air is, the more water vapour it can hold. If the air is made very hot by the sun in the daytime, and if there is such water near, with little wind, then the air, as the day goes on, comes to hold a large quantity of water-vapour. As the sun sets, the air quickly gets cooler. Then it cannot hold as much water-vapour as it did before, and so a good deal of the water-vapour turns into liquid drops and makes a mist.