Heat waves are among the most dangerous — and increasingly frequent — weather events in Spain. With temperatures that can exceed 45 °C in the southern peninsula, understanding their mechanisms, the highest-risk zones and protective measures is essential for getting through summer safely.

What is a heat wave?

AEMET defines a heat wave as an episode of at least three consecutive days in which maximum temperatures exceed the 95th percentile of the June-September historical series in at least 10 % of reference weather stations. In other words, a single extreme day does not qualify: the anomalous heat must be sustained over a wide area.

These episodes are typically caused by the northward expansion of the African ridge, a mass of hot Saharan air trapped at upper atmospheric levels beneath a powerful anticyclone. This configuration prevents cloud formation and blocks cooler Atlantic airflow.

Temperature records in Spain

  • Córdoba, August 2021: 46.9 °C, the highest temperature officially recorded by AEMET on the Peninsula.
  • Montoro (Córdoba), July 2017: 47.3 °C (secondary station).
  • Seville: regularly exceeds 45 °C during intense heat waves.
  • Murcia and Alicante: combine extreme temperatures with coastal humidity, pushing the heat index above 50 °C.
  • Zaragoza: the Ebro valley acts like an oven — warm air gets trapped between the Pyrenees and the Iberian System.

Highest-risk areas

The regions most exposed to intense heat waves are:

  • Guadalquivir valley (Córdoba, Seville, Jaén): the hottest area in Spain and all of Western Europe.
  • Ebro valley (Zaragoza, Lleida): a closed basin effect that accumulates heat.
  • Southern plateau (Ciudad Real, Toledo, Badajoz): extensive plains with no moderating maritime influence.
  • Southern Mediterranean coast (Murcia, Almería): when the terral (offshore westerly wind) blows, temperatures soar as the sea breeze is lost.

The urban heat island effect

In large cities, asphalt, concrete and the scarcity of green spaces generate the urban heat island (UHI) effect. Madrid, Barcelona, Seville and Valencia can register 4-8 °C more than suburban stations overnight. This prevents rest during the night and worsens health impacts, especially among the elderly.

Health impact and protective advice

  • Stay continuously hydrated: drink at least 2 litres of water per day, without waiting until you feel thirsty.
  • Avoid sun exposure between 12:00 and 18:00, the hours of peak radiation.
  • Wear light, loose, breathable clothing. Cover your head with a hat or cap.
  • Never leave children or pets inside parked vehicles: interior temperatures can exceed 60 °C within minutes.
  • Keep your home cool with shutters down during the day and cross-ventilation at night.
  • Watch over vulnerable people: over 65s, small children, those with chronic illnesses and outdoor workers.

Always check extreme temperature warnings on Meteo.es and the detailed forecast for your location to prepare for the toughest summer days.