The phenomenon could continue on May 31 (Saturday) and the following days, the health authority said in a note.

"A situation of poor air quality is expected on the mainland, with an increase in the concentrations of inhalable particles of natural origin in the air".

This pollutant (inhalable particles) has effects on human health, especially on the most sensitive population, such as children and the elderly.

While this phenomenon continues, the DGS recommends that the population avoid prolonged exertion, limit outdoor physical activity and avoid exposure to risk factors, such as tobacco smoke and contact with irritants.

Due to their greater vulnerability, children and the elderly, as well as people with chronic respiratory problems and cardiovascular patients, in addition to complying with the general recommendations, should, whenever possible, remain indoors, preferably with the windows closed.

In case of worsening symptoms, the DGS advises contacting the Health 24 Line (808 24 24 24) or, if necessary, seeking health services.

The health authority also says that the APA (Portuguese Environment Agency) website or the QualAr App can be consulted for "additional information on air quality and values ​​measured at monitoring stations".

The DGS also recommended preventive measures this week, such as drinking water, given the forecasts of rising temperatures in the coming days, which should reach values ​​above 30°C in most of the country.

According to the IPMA, Bragança, Évora, Guarda, Faro, Vila Real, Setúbal, Santarém, Lisbon, Beja, Castelo Branco and Portalegre are under yellow alert until 6 pm on Saturday due to the forecast of hot weather.