This situation is due to the positioning of the anticyclone west of the British Isles, "which extends in a ridge to the Madeira archipelago, transporting a mass of polar air in its circulation".

From Tuesday, the 18th, the mainland will begin to be influenced by a northerly flow and mass of cold air, "which will cause a significant drop in air temperature".

According to the IPMA, this change in weather patterns will bring low temperatures, lower than normal for this time of year. The cold will bring with it a decrease in cloud cover and rain.

Until Friday the 21st, minimum temperatures may drop between 2 and 4°C per day, reaching values ​​between 0 and -4°C in the interior North and Central regions, and between 4 and 7°C in the rest of the country.

Between the 19th and 20th, Wednesday and Thursday, the maximum temperature will drop, reaching values ​​between 6 and 10°C in the interior and between 12 and 15°C on the coast on the 21st.

Frost or ice formation is also expected, especially in the interior of the North and Central regions.

Rain and snow

Regarding rain, occasional light showers are expected, more likely at the end of the week, which will turn to snow in the higher areas of the Serra da Estrela mountain range. North winds will occasionally blow strongly on the coast and in the highlands.

Rain appears to be gradually returning to the mainland from North to South: it returns on Saturday to the districts of Braga, Porto, Vila Real and Aveiro; on Sunday to Coimbra, Santarém, Lisbon and Portalegre; and only on Monday to Évora and Faro.