Frost over central Mexico have a large impact on agriculture. During winter, frosts are associated with the passage of cold fronts. During summer, frosts are less frequent but their occurrence often results in a complete loss of maize crops.Sometimes, agriculturists in this part of the country are more concerned with frosts than with deficits in precipitation.
Frosts during summer are known as "unexpected frosts" since during this time of the year, minimum temperatures are usually above 6C. Most of the summer unexpected frosts are due to radiative cooling. The lack of moisture in the atmosphere may result in radiative cooling and minimum temperature changes of up to 10C in one day. Agriculture is planned in terms of probability of unexpected frosts based on historical records of minimum temperature. It is found that there is a period free of unexpected frosts from June through August. This period may be larger or shorter depending on whether it is an El Nino or La Nina year. An En Nino year results in drought over most of Mexico, a lack of moisture in the atmosphere and a short period free of frosts associated with radiative cooling. The opposite occurs during La Nina years. Such finding may be used in the planning of the agricultural cycle