Portugal braces for 42°C heatwave as IPMA issues yellow warnings across mainland districts

Peak temperatures and regional contrasts

Portugal faces its hottest day of the week on Thursday, 3 September, as continental temperatures climb across most districts. Forecasts from the Instituto Português do Mar e da Atmosfera (IPMA) indicate that maximum daytime values will range between 34°C and 38°C across the broader mainland territory. Interior regions situated south of the Serra da Estrela mountain range, including the Tejo Valley, Beira Baixa, and Alentejo, are set to experience peak levels between 40°C and 42°C. In contrast, the coastal strip will see milder conditions, with highs generally hovering between 25°C and 31°C, while southern coastal areas will record slightly higher values. Ahead of the surge, Wednesday minimums ranged between 13°C in Viana do Castelo, Braga, and Guarda and 20°C in Faro, with maximums reaching 37°C in Évora. Meteored Portugal indicated that conditions will intensify during peak afternoon periods:

During the hours of greatest heat, thermal anomalies should intensify, as maximum temperatures of around 42ºC are expected, especially in the Alentejo.

Yellow warnings and wildfire hazards

In response to the surge in heat, IPMA issued yellow weather warnings covering multiple administrative districts across continental Portugal. Depending on the reporting, between 11 and 14 districts are placed under alert, including Lisbon, Setúbal, Santarém, Évora, Beja, Portalegre, Castelo Branco, Guarda, Viseu, Vila Real, and Bragança. The yellow warning, which represents the least severe tier on Portugal's three-tier meteorological scale, applies when specific weather-dependent activities face operational risks. The warning is scheduled to take effect at 10:00 on Thursday (09:00 according to some notices) and remain active until 19:00 on Friday (18:00 in certain bulletins). Alongside the heat alerts, elevated temperatures have escalated the threat of wildfires. IPMA placed 30 municipalities across Bragança, Guarda, Coimbra, Castelo Branco, Santarém, Portalegre, and Faro under very high rural fire danger, with conditions worsening across the northern and central interior, Alentejo, and Algarve on Thursday.

Atmospheric dust and health recommendations

Meteorological models also point to the transport of airborne dust particles originating from North Africa, projected to affect southern sectors of mainland Portugal on Thursday. Ahead of the dust arrival, early Wednesday brought morning cloudiness across the northern and central regions before skies cleared. Public health advisories urge residents to take precautionary measures during the heat episode, placing a strong emphasis on maintaining frequent hydration. Authorities recommend avoiding direct sun exposure during peak daylight hours and postponing demanding physical exercise during the hottest intervals of the day. Vulnerable demographic groups, specifically infants, young children, the elderly, and individuals with chronic health conditions, require increased supervision and protective care to mitigate heat-related illness.

Outlook and gradual weekend cooling

A slight moderation of temperatures is forecast to begin on Friday, 4 September, across large swathes of the country, although the relief will remain limited in the interior. Inland districts are expected to remain close to 40°C, while the Douro Valley could see temperatures climb to 41°C, making it the warmest area in the country on Friday. A more pronounced drop in temperatures is projected to take place over the following days, primarily influencing the northern and central coastal regions. This subsequent transition will bring daytime temperatures back to seasonal norms, returning thermal anomalies in those sectors to neutral or negative values.