Portugal Heatwave Forecast: Up to 38°C From Saturday 19 September

Portugal is heading into a long hot spell in the second half of September, a fortnight that is normally substantially cooler than what is coming. IPMA, the national weather service, expects temperatures to climb from Saturday 19 September, with highs above 30°C across most of the mainland and close to 38°C in parts of the Alentejo and the Tejo valley. It rates the chance of an official heatwave across much of the country as high.

Fire danger comes with it: it was already very high to maximum in much of the interior and the Algarve this week, and on those days ordinary things like a countryside barbecue or strimming your land with a metal blade are banned. If you booked for a comfortable late-September week, or you live in a home that holds the heat, plan around both.

How hot will it get, and where?

IPMA’s notice of 16 September blames an anticyclone north of the Azores that is pushing hot, dry continental air over the Iberian Peninsula. From 19 September, temperatures rise gradually:

	What IPMA forecasts
Daytime highs	Above 30°C across most of mainland Portugal
Hottest places	Approaching 38°C, notably in the Alentejo and the Tejo valley
Nights	Not below 20°C in some places in the Alto Alentejo, Beira Baixa, the Tejo valley and the eastern Algarve
What stands out	How long it lasts, not how high it peaks

Nights that stay at 20°C or more are known in Portugal as noites tropicais (tropical nights). They matter more than they sound: as Observador notes, neither the ground nor the body cools enough before the heat returns, which raises the risk of fire and of heat-related illness.

The notice covers the mainland only. It gives no end date, and IPMA says it will update the notice if the picture changes, so check the latest version before you plan a week around the table.

Is this officially a heatwave?

Not yet, and it does not need 40°C to become one. IPMA counts a heatwave when, for six days in a row, the daily maximum is more than 5°C above the average maximum for that place and period. The yardstick is each place’s own climate for the time of year, so temperatures below this summer’s peaks can still make a heatwave in late September.

IPMA’s own summary: the peaks will be lower than some episodes this summer, but “substantially above” the averages for the second half of September.

Should you change your plans if you are visiting?

No need to cancel. Our best time to visit Portugal guide puts the second half of September among its three top picks of the year, and one hot spell does not change the averages behind that pick. What it changes is the shape of each day.

• Do the walking early and late. The DGS, Portugal’s health authority, advises staying out of direct sun especially between 11:00 and 17:00, with sunscreen of factor 30 or higher reapplied every two hours.
• Put inland hikes on hold. The guide already tells walkers to avoid inland trails in midsummer, when heat and wildfire risk peak, and the week ahead brings both. On very high fire-danger days some public forest areas are also off limits (see below).
• Drive in the cooler hours, and never leave anyone in the car. The DGS advises travelling at night where you can, and never leaving children, older or sick people in a vehicle standing in the sun.
• Build in cool indoor stops. Museums, cinemas and shopping centres are the DGS’s own suggestion for a few hours out of the heat.
• Keep babies and older relatives off the beach in the heat. The DGS says babies under six months should not be in the sun at all, and older people should not go to the beach on very hot days.

What should you do if you live here?

• Keep the heat out. Close the blinds and shutters. In the evening, once it is cooler outside than in, open up and let a draught through.
• Spend two to three hours a day somewhere cool. The DGS says this can prevent the worst effects of heat, particularly for children, older people and anyone with a chronic illness. The DGS also suggests finding out whether there are cooled shelters (abrigos climatizados) near you.
• Drink before you feel thirsty, and avoid alcohol and very sugary drinks. If you have a chronic illness, eat a low-salt diet or have been told to limit fluids, ask your doctor or call SNS 24 on 808 24 24 24 about how much to drink.
• Check on the people most at risk. Among the groups the DGS lists as most vulnerable are young children, older people, people with chronic heart, lung or kidney disease or diabetes, people taking some medicines (including for blood pressure, heart rhythm and depression, and diuretics), outdoor workers and anyone in poor housing.

What fire rules apply during the heat?

IPMA rates rural fire danger every day, municipality by municipality, on a five-step scale from reduzido (low) to máximo (maximum). You can check yours on IPMA’s fire-danger map. On 14 September, ANEPC, the civil protection authority, warned of very high to maximum danger, especially in the interior and the Algarve.

On any day your municipality is at muito elevado (very high) or máximo, the ICNF’s restrictions include:

Activity	Rule on very high or maximum days
Barbecues and portable grills in rural areas	Banned, except in places set up for them
Bonfires for leisure or festivities	Banned in rural areas
Smoking or any flame	Banned in rural areas and on the roads that border or cross them
Burning vegetation across open land (queimadas)	Banned
Sky lanterns and rockets	Banned; most other fireworks need town-hall authorisation
Strimmers with metal blades, scrub cutters and shredders, chainsaws, angle grinders	Banned in rural areas and around built-up areas; strimmers with nylon line are exempt
Priority prevention zones (APPS)	No entry to public or community forest, no organised events in forest areas, no drones overhead

If you have land, two more rules matter. Burning piles of cut vegetation needs authorisation or prior notice all year, registered in the Queimas e Queimadas app, and ANEPC’s 14 September warning said it is not allowed at all on very high or maximum days. Farm and forestry machines can still run on those days, but only from sunset until 11:00 and with the required safety equipment. Your câmara municipal (town hall) holds the maps of priority prevention zones, and the call centre listed on the ICNF’s rules is 808 200 520 or 211 389 320.

If the Government declares a situação de alerta (alert situation), its rules take priority over this table. It did so across the mainland from 3 to 6 July this year, banning entry to designated forest areas, burning, machinery work in forests, fireworks and sky lanterns.

What are the warning signs of heat illness?

	Heat exhaustion	Heat stroke
Signs	Intense thirst, heavy sweating, paleness, muscle cramps, tiredness and weakness, headache, nausea or vomiting, fainting	High fever; red, hot, dry skin with no sweating; a fast, strong pulse; headache, nausea, dizziness, confusion; partial or total loss of consciousness
What to do	Call a doctor or 112	Call a doctor or 112 immediately. Move the person somewhere cool, cool them with damp towels or cold water, fan them, and give nothing to drink if they are unconscious

Heat stroke needs medical help straight away. The DGS warns that once the body stops sweating, its temperature can reach 39°C within 10 to 15 minutes.

What should you do next?

• Visiting this week? Keep the trip and reshape the days. Our best time to visit Portugal guide has the region-by-region picture of when each part of the country is at its best.
• Moving around by car? Getting around Portugal covers the trains and coaches between cities, so the long hops do not have to happen behind a windscreen at 16:00.
• Living here and not sure where to go if someone feels unwell? Our healthcare guide explains SNS 24, health centres and hospital emergency departments.
• Checking the day ahead? IPMA publishes weather warnings by district and a daily fire-danger map by municipality.

This post is general information, not medical or legal advice. Forecasts and fire restrictions change day by day, so verify the current position with IPMA and your câmara municipal. For health advice call SNS 24 on 808 24 24 24; in an emergency, call 112.