Bragança and Guarda have been under an orange warning for persistent fog since 00:52 today, a level that will remain until 00:00 on December 27th, the IPMA said in a statement.

Vila Real and Viseu will be under a yellow warning over the same period, due to the forecast of persistent fog and cold weather, with the continuation of low temperature values, especially in places where the fog persists.

Yellow warnings relating to cold weather are also in force in Bragança and Guarda until Wednesday.

According to the most up-to-date information from IPMA, mainland Portugal will experience periods of very cloudy skies today, becoming slightly cloudy or clear in the South region from late morning onwards.

According to IPMA, the weather during the Christmas period will be influenced by an anticyclone, located northeast of the Azores and extending to the northern part of the Iberian Peninsula.

The nights will be cold, with a minimum temperature above 5 degrees Celsius (ºC) only on the coastal strip and conditions for ice and frost formation, especially in the northern and central interior where the minimum temperature is expected to register values between -4 and 0°C .

The maximum temperature should generally register values between 10ºC and 20°C, with the highest values on the coast of the Central and South regions, particularly in the Algarve, being lower than 10°C in the interior of the North and Center regions .

In places where cloud cover or fog persists, temperature values below 5°C should persist.

The institute also warns of the need for care in terms of road safety, particularly during the night and morning, which is likely to be affected by the occurrence of ice on the road and fog.