Outdoors in Lisbon or the Algarve today? North African dust is in the air until Tuesday
Portugal's health directorate expects poor air quality on 14 and 15 September across Lisbon and the Tagus Valley, the Alentejo and the Algarve, with PM10 climbing. Then the heat breaks, and on the coast Tuesday's high falls by as much as nine degrees.
An air mass off the North African deserts is crossing mainland Portugal on Monday and Tuesday, carrying suspended dust with it. Portugal’s health directorate has issued the notice it puts out for these episodes, and this one is aimed at the southern half of the country: Lisbon and the Tagus Valley, the Alentejo and the Algarve above all.
What rises is PM10, the inhalable particles that occur naturally rather than coming out of an exhaust or a chimney. Saharan dust, in other words. It still reaches your lungs, and children and older people feel it first.
What the DGS is asking for
Everyone: skip prolonged exertion, keep physical activity indoors where you can, and stay away from other irritants, tobacco smoke included. Children, older people, anyone with a chronic respiratory condition — asthma is named explicitly — and cardiovascular patients: stay inside where that is workable, ideally with the windows shut. Ongoing treatment continues as normal. If symptoms get worse, the instruction is to call Linha Saúde 24 on 808 24 24 24 or go to a health service. Station-by-station readings are published on the Portuguese Environment Agency’s QualAr portal.
This is the second such notice this month. The previous one covered 3 September and reached most of the country, with the centre and south worst affected. Late-summer Saharan dust over Portugal is ordinary enough. Two episodes in eleven days is the part worth registering.
Then the heat splits in two
Monday was one of the hottest days of the month, with 38C in Évora and Santarém. From Tuesday the map divides. On the coast the high collapses: Santarém goes from 38 to 30, Lisbon from 35 to 29, Coimbra from 34 to 26, Leiria from 33 to 24. Aveiro tops out at 23 and Porto at 24.
Inland you would barely know. Castelo Branco and Évora still reach 37 on Tuesday, Beja 35, Bragança and Faro somewhere around 34. The wind swings to the north and north-west on Tuesday and Wednesday, and that swing is the whole difference between standing on the beach and standing fifty kilometres inland. If this is starting to feel like a summer that will not end, it is worth rereading why WHO Europe now treats extreme heat as a public-health emergency and how western Europe recorded its hottest summer ever without Portugal appearing on a single list.
File image (January 2022): Copernicus Sentinel-3 / European Union — contains modified Copernicus Sentinel data 2022
