Events

Heatwaves in the summer of 2025

Heatwaves during the summer months (June, July and August) are the most noticeable and have the greatest impacts when they occur in this period, although, according to the definition of the Heat Wave Duration Index (HWDI), they may occur at any time of the year.

In the summer of 2025, there were 3 heatwaves: the first between 15-20 June, the second between 26 June - 9 July, and the longest of the summer, between 29 July and 17 August.

The third heatwave of summer 2025 was exceptional in terms of its duration, lasting between 6 and 17 days depending on the region. It was the longest heatwave ever recorded in mainland Portugal affecting the northern and central regions of the territory.

In terms of average cumulative temperature magnitude, across mainland Portugal, this third heatwave reached a value of 78.8 °C.

October 2025 - the 6th heatwave in mainland Portugal

In 2025, mainland Portugal recorded at least six heatwaves so far, characterized by exceptionally high maximum temperatures, with notably prolonged and intense episodes in late June and between July and August — the latter being the longest ever recorded in the northern and central inland regions (July 29 to August 17).

In early October, a new and unusual prolonged warm spell occurred, marking the sixth heatwave of the year, which lasted from October 10 to 19 and affected 65% of meteorological stations. The regions most impacted were Lisbon and the Tagus Valley, much of the North (Trás-os-Montes and Alto Douro), and parts of Upper and Central Alentejo. The stations of Mora, Pegões, Torres Vedras (Dois Portos), and Rio Maior recorded nine consecutive heatwave days, reflecting the exceptional persistence of this event, which occurred outside the usual period of intense heat in mainland Portugal.