Portugal Faces Week of Extreme Heat as Lisbon and Three Other Districts Enter Red Alert With 43°C Possible in Alentejo

Red alerts issued as extreme heat grips Portugal

Portugal is entering a prolonged period of extreme heat, with the hottest conditions expected to last at least a week. The Portuguese Institute for Sea and Atmosphere, IPMA, has raised warnings to red for four districts as maximum and minimum temperatures remain exceptionally high.

Lisbon, Portugal, and Setúbal, Portugal, will be under red warning from midnight on Thursday until the end of Friday. Coimbra, Portugal, and Leiria, Portugal, will also be under red warning on Friday and Saturday because of hot and dry weather.

The red warning is the highest level on the IPMA scale. It signals an extreme weather risk situation.

The heat will not be brief.

Across mainland Portugal, maximum temperatures are expected to exceed 35 degrees Celsius, while inland and southern areas will be hotter. In parts of Alentejo, Portugal, temperatures could reach 43 degrees Celsius at least until Monday of next week.

Orange warning expands across mainland Portugal

Castelo Branco, Portugal, Portalegre, Portugal, Évora, Portugal, and Beja, Portugal, are already under an orange warning this Wednesday.

Orange is the second-highest level on the IPMA warning scale and indicates a moderate to high weather risk situation.

By Friday, the orange warning will extend to all of mainland Portugal. That means the heat risk will no longer be limited to the hottest inland districts, but will cover the entire mainland territory.

Heat will spread across the map. The warning zone will widen. Day after day, the same hot pattern will remain in place.

Nights will stay unusually warm

The heatwave will be dangerous not only because of the daytime maximums. Night-time temperatures will also stay high.

Minimum temperatures will remain above 20 degrees Celsius across much of mainland Portugal. In some regions, temperatures may not fall below 24 to 28 degrees Celsius for several nights.

Greater Lisbon, Portugal, is among the areas where nights could remain especially warm.

This matters because the body needs cooler nights to recover from daytime heat. When the air stays hot after sunset, homes, streets and buildings release stored heat slowly. The atmosphere remains heavy, even in the dark.

Coastal areas face rare heat pattern

IPMA says the episode is particularly unusual when compared with the normal climate of mainland Portugal, especially in coastal regions.

In a statement, the meteorological institute explained that the lack of inland penetration of the sea breeze, or its weak intensity, will help maintain high temperatures over several consecutive days.

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

Coastal districts often receive some relief from the Atlantic breeze. This time, that cooling influence will be limited in places, allowing the heat to build and persist.

Anticyclone drives the hot weather pattern

The hot weather over mainland Portugal is being influenced by an anticyclone located to the north and northwest of the Azores archipelago, Portugal.

This kind of high-pressure system can favour settled weather, stronger sunshine and weak air movement. Under those conditions, temperatures can rise quickly during the day and remain elevated at night.

The pattern is stable. The air is hot. The cooling mechanisms are weak.

For mainland Portugal, that combination means several consecutive days of very high temperatures, especially away from the immediate influence of the Atlantic.

Very high to extreme UV levels expected

IPMA also warns that the very hot weather will be accompanied by very high to extreme ultraviolet radiation levels in the coming days.

Across mainland Portugal, very high UV Index values are expected in all districts up to Friday, 3 July. Values will range from 10, classified as very high, to 11, corresponding to an extreme level.

The strongest ultraviolet radiation occurs around solar noon. In mainland Portugal, IPMA says solar noon is reached at around 1.30 pm at this time of year, with slight variation by latitude and a small increase of a few minutes from north to south.

IPMA advises avoiding sun exposure during peak hours

IPMA advises against sun exposure around solar noon, when the UV Index reaches its maximum.

The institute recommends avoiding sun exposure as much as possible, especially between 11 am and 4 pm. It also advises using sunglasses with a UV filter, a hat, a T-shirt, a parasol and sunscreen.

The main warnings for the coming days are:

• Red warning for Lisbon and Setúbal from Thursday through Friday
• Red warning for Coimbra and Leiria on Friday and Saturday
• Orange warning expanding to all mainland Portugal on Friday
• Maximum temperatures above 35 degrees Celsius across the country
• Temperatures above 40 degrees Celsius especially inland and in the south
• Up to 43 degrees Celsius possible in Alentejo at least until Monday
• Minimum temperatures above 20 degrees Celsius across much of the mainland
• Very high to extreme UV levels through Friday, 3 July