The Portuguese Institute of the Sea and the Atmosphere (IPMA) says the yellow warning for precipitation will take effect at 6am in the districts of Viana do Castelo, Braga, Porto, and Aveiro.

In these four districts, a yellow warning for thunderstorms will also be in effect, given the "favourable conditions" for rainfall accumulation of 10 to 20mm per hour and wind gusts of 70 to 90 km/h.

The yellow warning will be in effect until 12pm in Porto and Aveiro and until 3pm in Viana do Castelo and Braga.

At 9am, the yellow warning for precipitation will be extended to five more districts - Vila Real, Viseu, Leiria, Coimbra, and Lisbon, with the thunderstorm warning also in effect in the latter three. The notices will be in effect until 3pm.

From 12pm, the districts of Bragança and Guarda will also be under a yellow warning due to periods of rain or showers, which may be heavy at times and accompanied by thunderstorms. The warning should be cancelled at 6pm.