Frost forms when the temperature drops below 32 degrees Fahrenheit. In order for frost to form, other conditions have to be present as well.
Besides an air temperature of at least 32 degrees F, frost needs humid air to form. Frost forms on objects when water vapor in the air condenses close to or on the ground. Farmers have developed ways of predicting and preventing the formation of frost on crops. They take into account different aspects of weather such as humidity, wind, clouds and the dew point to determine if there will be a frost.
To prevent frost damage, farmers add extra mulch to crops, harvest crops like tender vegetables and flowers early and use machines to deliver heat to plants typically in greenhouses or other structures.