The yellow warning for the north coast of Madeira and Porto Santo and the districts of Viana do Castelo, Porto, Aveiro, Coimbra, Leiria, Lisbon, Setúbal, Beja and Faro, on the mainland, will be in force until 18:00 on Saturday.
According to the IPMA is expected strong sea disturbance, with northwest waves with 4 to 5 meters.
The yellow warning is issued by IPMA whenever the weather situation represents risk for certain activities.
Because of the sea disturbance, the bars of Caminha, Esposende, Vila Praia de Âncora, Póvoa de Varzim and Vila do Conde are closed to all navigation, according to the Portuguese Navy's website.
The bar of Figueira da Foz is closed to vessels less than 35 meters long.
The IPMA forecasts for 7 January on the continent little cloudy or clear sky, the possibility of periods of light rain on the coast north of Cabo Raso until early morning, fog or mist in the morning, ice formation and frost in particular in the interior North and Centre and a small rise in maximum temperature.
It is also expected weak to moderate north winds, gradually shifting to the northeast, blowing moderate to strong in the western coastal strip and the highlands until late afternoon.
The minimum temperatures on the mainland will range between 0 degrees (in Guarda and Bragança) and 8 (in Lisbon) and maximum between 7 (in Guarda) and 17 (in Faro).
The IPMA forecasts for 7 January in the archipelago of Madeira generally cloudy sky, periods of rain or showers, more frequent in the north and highlands and a small rise in temperature.
The forecast also points to moderate northeasterly wind, being moderate to strong and with gusts up to 60 kilometres per hour in the highlands.
In Funchal, temperatures will vary between 16 and 22 degrees Celsius and in Porto Santo between 16 and 19 degrees.