If a ranking of the most feared meteorological phenomena had to be made, frost would be near the top. When the temperature descends sharply to the freezing point,it can destroy complete crops in a single night,especially if it occurs in a flowering or sprouting period,causing immediate and sometimes irreversible damage.

This happens because when the low temperature reaches 0°C, the water contained in plants, on the ground, and in the air begins to freeze. When these conditions last for many hours, everything affected by the frost seems to have been “burned,” as its affect is frequently enough described.

Not All Frosts Are Equal

“When low temperatures hit 0°C, water in plants, ground, and air freezes, causing what looks like ‘burn’ damage.”

There are different types of frost, according to the mechanism that generates them. In the central area of Chile, they are usually registered between May and August, although they can also occur in the early spring. The most common are frosts due to advection and radiation.

An advection frost occurs when a mass of cold air-usually of polar origin-moves across the continent, causing an abrupt drop in temperature. It is indeed usually accompanied by wind, which makes it easier for the cold to spread through large areas. low temperatures can last all night, several nights in a row, and even during the mornings.

These types of frosts are usually the most harmful,since they are associated with dry and cold air conditions. They are the so-called “black frosts,” since ice is not seen on the surface, but the cold directly affects the internal structure of the plants, breaking their cells and causing their darkening, as if they were burned.

Meanwhile, radiation frosts occur on clear and windless nights, when the earth’s surface loses heat towards space. Without clouds that act as a thermal blanket, soil cooling is more severe, and temperatures near the ground level can fall below zero, even though the air higher up remains warmer.

In Chile, this type of frost predominates at the end of autumn, during the winter, and early spring. It is characterized by covering the surface with ice; hence, they are known as “white frosts.”

Another less common type is frost by evaporation, which is produced when the evaporation of moisture in the soil or vegetation causes cooling, leading the temperature to fall to the freezing point. They occur in specific conditions, such as after rains, which are followed by dry and cold winds.

Why Are Frosts Crucial?

Along with affecting agriculture,frosts involve risks to human health,especially in vulnerable populations,since cases of respiratory diseases and complications associated with extreme cold increase.

In urban areas, frost can also cause ice formation on roads and paths, increasing the risk of accidents. And in rural areas, they can freeze pipes, irrigation systems, or affect cattle.

Although at present,the frequency of frost is decreasing in almost all regions of medium and high latitudes due to the increased warm nights linked to climate change,frosts will not disappear fully due to the natural variability of the weather.

It may happen that the frost-free season extends, but the risk of late or sporadic frost will continue to be relevant.