In a statement published on its website, the Instituto Português do Mar e da Atmosfera (IPMA) explains that this drop in temperature is due to the passage of “cold front that crosses the territory from north to south, bringing masses of polar air from the northwest”.
According to the IPMA, this "gradual decline" in temperature will initially be felt in the North and Center regions, extending to the entire country by Wednesday.
“On the 18th and 19th [Wednesday and Thursday], the minimum temperature values in most of the country should be below 5°C, except on the coast (between 5°C and 8°C), being lower in the interior North and Center, in the order of -5 C to 0° C”, reads the same note.
The maximum temperature values “should not exceed 11º C/14º C, being lower in the interior North and Center” (5º C to 9º C).
Also according to the IPMA note, these weather conditions will give rise, as early as Sunday, to precipitation, especially in the North and Center regions, with greater incidence in Minho and Douro Litoral, and to snowfall in the highlands.