Portugal braces for unseasonal storms, 90 km/h winds, and temperature drops
An unseasonal Atlantic depression will bring heavy showers, thunderstorms, and winds of up to 90 km/h across mainland Portugal starting on 23 August 2026.
Approaching depression and yellow alerts
Mainland Portugal will experience a sharp transition in weather conditions beginning on Sunday, 23 August 2026, as an Atlantic low-pressure system and an associated cold front move toward the western Iberian coast. The Portuguese Institute for the Sea and Atmosphere placed eight continental districts under a yellow weather warning for thunderstorms between 09:00 and 18:00 on Sunday. The affected districts are Porto, Setúbal, Lisbon, Viana do Castelo, Leiria, Aveiro, Coimbra, and Braga. Forecasters expect persistent and heavy showers accompanied by wind gusts reaching up to 90 kilometres per hour, particularly in coastal and northern regions.
Instituto Português do Mar e da Atmosfera meteorologist Cristina Simões described the incoming atmospheric system as unusual for late August.
We are facing a depression that is west of the mainland territory and approaching.
Weekly rainfall and cooling trend
The low-pressure system will move northeast into Spanish territory on Monday, 24 August 2026, but atmospheric instability will persist across Portugal through Sunday, 30 August 2026. A second cold frontal surface moving southeast will approach the western coast on Wednesday, bringing renewed bursts of heavy rain. Precipitation will concentrate across the Northern and Central regions, with the highest totals anticipated in Minho and Douro Litoral. Southern areas will remain comparatively sheltered, though they will still receive lighter rainfall from Minho down to the western Algarve.
- Yellow weather warning takes effect across eight mainland districts for thunderstorms and strong winds
- Yellow weather warning concludes for coastal and central districts
- Depression tracks northeast into Spanish territory while heavy rain continues in northern Portugal
- Cold front approaches western coast to bring renewed precipitation to Minho and Douro Litoral
- Low-pressure system over mainland Portugal expected to subside
Temperatures will drop across the country following multiple heatwaves earlier in the summer. Coastal areas will see maximum temperatures between 20 °C and 25 °C, while inland regions will reach 28 °C to 30 °C, with temperatures above 30 °C largely restricted to parts of the Alentejo near the border with Spain. Overnight minimum temperatures will range from 12 °C to 18 °C during the first half of the week before dropping further to between 9 °C and 16 °C later in the period.
Civil Protection safety guidance and environmental risks
The National Civil Protection Authority issued a safety alert on Saturday afternoon, warning residents of risks linked to flash flooding, soil infiltration, and falling debris. Officials advised against walking or driving through flooded areas, securing loose structures such as scaffolding and signs, and moving vehicles and livestock out of flood-prone zones. Drivers were urged to adopt defensive driving practices on wet roads, while pedestrians should avoid lingering near trees due to gusty winds. Along the coast, maritime conditions will deteriorate as sea swells shift from the northwest to the southwest, generating waves up to three metres high.
The return of heavy rainfall follows a severe summer fire season that burned approximately 63,000 hectares of vegetation across Portugal since the start of 2026. Environmental authorities expressed concern that rainwater will wash ash and loose sediment from bare hillsides into river basins, threatening water supply quality in affected municipal reservoirs.
