Portugal prepares for rising temperatures and likely heatwave

By Lina Ferreira

Published on 18/09/2026 - 11:48 GMT+2

Portugal is set to experience a gradual rise in temperatures from this Saturday, with weather conditions hotter than usual for this time of year. The warning comes from the Portuguese Institute for Sea and Atmosphere (IPMA) (source in Portuguese), which is even pointing to the likelihood of a heatwave.

"This spell of hot weather will be defined mainly by how long it lasts, with a high probability that it will develop into a heatwave across much of the country," the IPMA said in a statement.

The document explains that a heatwave occurs when, "over a period of six consecutive days, the maximum air temperature is 5 °C above the average value of the daily maximum temperatures".

Temperatures are therefore expected to reach above 30 °C in mainland Portugal. In some areas, such as Lisbon and the Tagus valley, they could even approach 38 °C.

Minimum temperatures will also rise, staying above 20 °C in some parts of Alto Alentejo, Beira Baixa, the Tagus valley and the eastern Algarve.

"Although the forecast maximum temperatures are lower than those recorded during some episodes this summer, they will be substantially higher than the average for the second half of September," the statement adds.

The hot weather is due to the "influence of an anticyclone located to the north of the Azores, extending in a ridge as far as the Bay of Biscay". This system will transport "a mass of continental air (hot and dry) over the Iberian Peninsula".

In July, Portugal had already recorded anomalous temperatures, with red warnings in most of the country and the government declaring a state of alert. The same situation extended to the rest of mainland Europe during the month of July.

A report by the non-profit organisation Climate Central concluded that the continent had been "the most abnormally warm region on the planet". Almost nine in ten Europeans lived through an entire month of "dangerous heat".