Understanding La Niña and Its Impact on Mexico
Dr. Alejandro Jaramillo Moreno, a researcher at the Institute of Atmospheric and Climate Change (ICAyCC) at UNAM, has announced that Mexico’s upcoming winter season (2025-2026) will feature dry conditions and significant temperature variability, a trend attributed directly to the climate phenomenon known as La Niña.
La Niña is characterized by the cooling of the eastern equatorial Pacific Ocean surface, which disrupts global atmospheric circulation patterns and alters rainfall and temperature in various regions worldwide.
Effects of La Niña on Mexico
Jaramillo Moreno explained that, in Mexico, La Niña causes reduced rainfall and mostly clear skies, particularly in the northern and central parts of the country, along with a lower frequency of cold fronts.
The winter season in the Northern Hemisphere spans December, January, and February. The cold front season begins in autumn and extends into spring, influencing rainfall and temperature drops—crucial sources of precipitation in northern Mexico. However, when La Niña intensifies, its reduced frequency leads to droughts in central Mexico as well.
“The behavior and quantity of cold fronts are directly related to changes in atmospheric circulation in the Northern Hemisphere, particularly the mid-latitude jet stream… Under La Niña conditions, the jet tends to shift northward and become more wavy,” explained Dr. Jaramillo Moreno from ICAyCC.
He further elaborated that this results in cold fronts taking more northerly paths, causing more damage to central and northwestern United States. Consequently, fewer cold fronts reach Mexico, reinforcing a drier winter.
Characterizing a Dry Winter
A dry winter, according to Jaramillo Moreno, is marked by scant rainfall and clear skies, leading to significant temperature drops at night and mild or even warm conditions during the day. This pattern results in frequent temperature changes rather than prolonged periods of continuous cold.
Alongside a few cold fronts that have entered the country—such as fronts 30 and 31 of this season—a polar air mass and the third winter storm have caused intense temperature drops, although extreme cold episodes were more sporadic than in typical winters.
Although Mexico’s rainy season primarily occurs in summer, winter can still see associated precipitation from cold fronts. These winter storms form when cold air masses displace warmer air to higher atmospheric levels, promoting cloud formation and rainfall outside the usual period, as explained by Dr. Alejandro.
Recommendations for the Mexican Population
Given the season’s minimum temperatures, Dr. Jaramillo Moreno advises the population to stay informed with official forecasts and alerts and take preventive measures to protect against cold temperatures, especially vulnerable individuals. He also warns about the alternation between cold and mild days that can lead to periods of poor air quality.
Key Questions and Answers
- What is La Niña and how does it affect Mexico’s winter? La Niña is a climate pattern characterized by the cooling of the eastern equatorial Pacific Ocean surface, which disrupts global atmospheric circulation patterns. In Mexico, La Niña causes reduced rainfall and mostly clear skies, particularly in the northern and central parts of the country, along with a lower frequency of cold fronts.
- What are the characteristics of a dry winter in Mexico? A dry winter is marked by scant rainfall and clear skies, leading to significant temperature drops at night and mild or even warm conditions during the day. This pattern results in frequent temperature changes rather than prolonged periods of continuous cold.
- What recommendations does Dr. Jaramillo Moreno provide for the Mexican population during this winter? Dr. Jaramillo Moreno advises the population to stay informed with official forecasts and alerts, take preventive measures against cold temperatures—especially for vulnerable individuals—and be aware of the alternation between cold and mild days that can lead to periods of poor air quality.
