Mexico’s Record Heat: Föhn Effect Explained

Mexico — Since late April and early May, a significant temperature increase has been observed in central and southern Mexico. Experts attribute this phenomenon to a combination of the Föhn effect—a warm, dry wind descending from mountains—and the presence of an anticyclone in the mid-levels of the atmosphere. These factors have driven temperatures to record highs, with Axtla de Terrazas in San Luis Potosí registering 46°C on May 6.

The Science Behind the Heat

The Föhn effect is a classic meteorological phenomenon in mountainous regions. Moist air rises on the windward side of a mountain range, cools, and releases precipitation. As it descends on the leeward side, the air compresses, dries, and heats rapidly. In recent days, this descending wind has been active along the Gulf of Mexico, pushing temperatures to unprecedented levels.

Meanwhile, the anticyclone stabilizes the atmosphere, suppresses cloud formation, and traps hot air near the surface. These conditions typically precede the arrival of a cold front, acting as an intense prelude to polar air influx.

Not a Traditional Heat Wave

Meteorologists clarify that this event does not qualify as a prolonged heat wave, which requires several consecutive days of abnormally high temperatures. Instead, it is a seasonal spike driven by the Föhn effect. While the National Meteorological Service (SMN) reports a “heat wave” affecting Mexico City and the State of Mexico with highs of 29–31°C, experts like meteorologist José Martín Cortés emphasize that the current heat aligns with typical spring patterns rather than an atypical climatic event.

Record-Breaking Temperatures

Recent and forecasted temperatures highlight the severity of the event:

• San Luis Potosí: Axtla de Terrazas reached 46°C on May 6.
• Oaxaca: Expected highs of 40–45°C.
• Veracruz: Projected highs of 40–45°C in southern and central regions.
• Tabasco: Eastern areas may see 40–45°C.
• Mexico City: Cloudier skies keep highs lower (30–35°C).

Gulf and southeastern states report the highest values (40°C or above), while central regions range from 35–40°C—exceeding typical spring averages.

Yucatán Also Affected

Yucatán experienced extreme heat this week due to the same phenomena. On May 7, temperatures in the state’s south and southwest peaked at 44°C, with heat indices surpassing 46°C, marking one of the year’s hottest days. In Mérida, temperatures fluctuated between 37°C and 43°C, with a perceived heat of 51.5°C. Local authorities issued extreme heat alerts, advising residents to avoid sun exposure between 11:00 AM and 4:00 PM, stay hydrated, and monitor vulnerable groups like children and the elderly.

Environmental and Social Impacts

Droughts and Wildfires

The extreme heat exacerbates existing drought conditions. According to Conagua, over 65% of northern municipalities already face some drought severity. Low humidity and warm winds heighten wildfire risks, with authorities warning that strong winds could accelerate fire spread. Ecosystems are under strain: water reserves dwindle, crops suffer, and vegetation becomes more flammable.

Health Risks

High temperatures increase health hazards, including heatstroke, dehydration, and aggravated chronic illnesses. Vulnerable populations—children, the elderly, and the sick—require special attention. Officials recommend continuous hydration, limited sun exposure, and lightweight clothing.

Daily life is disrupted as outdoor work productivity declines, electricity demand surges for cooling, and transportation systems face strain.

Official Warnings and Recommendations

The SMN and Conagua have issued alerts, confirming the heat wave’s impact across 21 states. Authorities urge precautions, particularly avoiding peak sun hours (11:00 AM–4:00 PM) and prioritizing hydration. The heat is expected to persist until a cold front arrives later in the week.