This time the dust will be less than last week when the Saharan “clay rain” covered the country, according to the Portuguese Institute of the Sea and the Atmosphere (IPMA).

The IPMA predicts the dust concentration "to be characterised as a normal episode, with an intensity similar to those that occur with some frequency over the skies of the Iberian Peninsula".

The IPMA says that the phenomenon will be more noticeable until the beginning of Saturday, but the rain will "help to reduce the concentration of dust near the surface", making it "hardly visible in several areas of the country"

According to the Portuguese Institute of the Sea and Atmosphere, the situation "is caused by the circulation of dust at altitude", in which there is "a flow from North Africa originated by a depression located southwest of the continent's territory".

On Saturday, the dust is to dissipate, as "the depression will move progressively to the east, leading to a change in the circulation pattern".