Fifteen Spanish regions on alert as September heatwave reaches 42 degrees

Rising temperatures and widespread warnings

The State Meteorological Agency placed 15 autonomous communities in mainland Spain on yellow and orange heat alerts as an unseasonal warm episode expanded across the country. The temperature surge began on Wednesday, 2 September, following a brief cooling period at the end of August. Meteorologist Mario Picazo noted that daytime maximums would consistently exceed 40 degrees Celsius in several provincial capitals during the first weekend of September. Warm southerly air flows drove interior temperatures between 5 and 10 degrees Celsius above seasonal averages. The agency projected that the thermal episode would persist through early the following week until Tuesday.

Mario Picazo outlined the trajectory of the late-summer warm front for Eltiempo.es.

Heading into the first weekend of September, we are once again going to see daytime temperatures exceeding 40 degrees in some provincial capitals.

Regional distribution of maximum heat

Interior river basins and southern regions registered the highest readings during the opening days of the episode. On Thursday, temperatures reached 42 degrees Celsius in Ciudad Real and in the Guadalquivir valley, while the Tagus and Guadiana valleys experienced similar afternoon conditions. Orange alerts applied to Andalusia, Castilla-La Mancha, and Extremadura, covering provinces such as Cadiz, Cordoba, Huelva, Jaen, Seville, Toledo, Badajoz, and Caceres. Maximum temperatures rose by five degrees in Badajoz and reached 32 degrees Celsius in Bilbao. High pressure maintained mostly clear skies across the peninsula, though low cloud cover formed along the Alboran coastline and the Cantabrian coast. Northeast depressions and the Ebro valley approached 37 degrees Celsius on Thursday before climbing above 40 degrees Celsius on Friday.

Nocturnal conditions and equatorial nights

Elevated temperatures persisted overnight across large portions of Spain. Tropical nights, defined by minimum temperatures remaining at or above 20 degrees Celsius, became widespread throughout the southern half, the Mediterranean coastline, and the northeast. In Barcelona and parts of the southwest quadrant, nighttime minimums reached 25 degrees Celsius. Mario Picazo identified equatorial nights, where readings fail to drop below 25 degrees Celsius, in coastal areas such as Cadiz. Minimum readings in the Canary Islands and parts of the southwest also remained at or above 25 degrees Celsius on Friday. These warm nights were accompanied by increasing cloud cover and suspended atmospheric dust drifting in from the southwest.

Forecast progression and approaching Atlantic front

High temperatures are forecast to maintain stability over most of the interior through Friday, alongside the formation of dry thunderstorms in interior mountain ranges. Temperatures in the eastern Cantabrian area, the eastern thirds, and the northern plateau continue to climb, while northern Galicia and the southwestern third register modest initial drops. Conditions will shift progressively over the weekend as Atlantic air begins to alter weather patterns in the northwest. Frequent rainfall is expected in Galicia on Saturday, followed by a frontal system arriving on Sunday that brings cooler air and increased atmospheric instability. The meteorological agency projects that the broader warm pattern will hold over the rest of the peninsula until Tuesday.