Extreme heat: Portugal under red alert until Sunday

The Portuguese Institute for Sea and Atmosphere (IPMA) has placed 12 of mainland Portugal's 18 districts under a red alert (the highest level on the scale, which signals an "extreme weather risk situation"), from Thursday and at least until Saturday, because of the forecast heat, with the "persistence of extremely high temperatures, both daytime highs and night-time lows".

The red alert for heat will be extended from this Thursday to the districts of Beja, Évora, Portalegre and Santarém, as well as Lisbon and Setúbal, and on Friday it will be widened to Aveiro, Braga, Porto and Viana do Castelo, along with Coimbra and Leiria.

The remaining six mainland districts – Bragança, Castelo Branco, Faro, Guarda, Vila Real and Viseu – will be under an orange alert (the second-highest level on the scale, signalling a "weather situation of moderate to high risk") between Thursday and Saturday, according to IPMA.

The previous weather forecasts, issued on Wednesday, had only the districts of Lisbon and Setúbal under a red alert for heat from Thursday, extending on Friday to Coimbra and Leiria.

In a statement, IPMA says a "prolonged spell of very hot, dry weather" is expected, with maximum temperatures reaching between 35 and 41°C across most of the country, and between 41 and 44°C in the Tagus valley and the Alentejo.

"Minimum temperatures will remain above 20°C in much of the mainland, and there will be areas where temperatures are not expected to fall below 24 to 28°C for several nights, including Greater Lisbon," the Portuguese meteorological institute adds.

IPMA explains that, "compared with the usual climate in mainland Portugal", the situation will be particularly abnormal in coastal regions, "where the lack of penetration of the sea breeze inland and/or its weak intensity will contribute to high temperatures over several consecutive days, leading to a rare situation in some places".

Weather conditions in mainland Portugal are being influenced by an anticyclone located to the north/northwest of the Azores archipelago and, according to IPMA's forecasts, this extreme heat episode is expected to last for at least a week.

IPMA has also warned of very high to extreme ultraviolet index values. Across the mainland, up to Friday 3 July, very high levels are expected in all districts, ranging from a UV Index of 10, classified as very high, to a UV Index of 11, which is considered extreme.

The authorities advise against exposure to the sun, especially around solar noon, when the UV Index reaches its peak, and they recommend the use of sunglasses with UV filter, a hat, T-shirt, sunshade and sunscreen.