Portugal is set for a sharp change in weather, moving from an unusually warm and dry start to November to colder nights and a return of rain. The transition is expected to happen in two stages: temperatures will drop from Tuesday, followed by increasingly frequent precipitation from Friday onwards.
The fall will be noticeable during both the day and night. In Lisbon, the forecast maximum drops from 26 °C to 22 °C on Tuesday and 19 °C on Thursday. Évora is expected to decline from 27 °C to 24 °C and then 20 °C, while Porto is forecast to fall from 23 °C to 19 °C and then 17 °C.
Inland areas may record sub-zero temperatures overnight, particularly on Thursday. Bragança could fall slightly below 0 °C, while frost is likely in valleys and sheltered locations across the north and centre during Wednesday and Thursday. Forecast minimums include around 5 °C in Évora, 7 °C in Coimbra and 9 °C in Lisbon.
The colder conditions are linked to an incursion of continental air from eastern Europe and Russia. A strong anticyclone near the British Isles is favouring easterly winds, allowing colder, drier air to move towards western Europe and reach Portugal. The air will be modified during its journey and is expected to arrive less cold than in its source region.
Rain may begin with some showers in northern areas on Thursday, while Friday is expected to bring a greater likelihood of more frequent precipitation. Forecast probabilities cited for Friday are 51% in Porto, 41% in Coimbra and 35% in Lisbon.
The signal becomes stronger during the weekend. For Saturday, the reported probabilities are 84% in Porto, 76% in Coimbra and 75% in Lisbon. On Sunday, they rise to around 90% in some areas, including 82% in Lisbon, while further increases are expected on Monday and Tuesday.
The forecasts indicate a strong possibility of rain across the country at the start of next week. On Monday, probabilities reach 100% in locations including Porto, Coimbra, Santarém, Lisbon, Évora and Faro, with 98% forecast for Guarda and Bragança. Similar values are expected on Tuesday, followed by a continued strong signal on Wednesday.
These percentages indicate the likelihood of rain occurring at some point during the day, not that it will rain continuously or intensely. The precise timing, intensity and trajectory of the Atlantic systems remain uncertain, as does whether they will develop into a storm affecting Portugal.
The Azores are expected to continue experiencing periods of rain linked to Atlantic disturbances. In Madeira, further precipitation is possible after heavy rain on Sunday caused damage, with some scenarios indicating increased instability during the weekend. The intensity cannot yet be determined.
The continental air will initially bring clear, dry and very cold nights. Once Atlantic air returns, rain, wind and humidity may make conditions feel more uncomfortable even if overnight temperatures rise, as clouds can reduce surface cooling while wind and wet clothing increase heat loss.
Sources: Observador.