"After a long period of relatively low temperatures for the time of year, it is expected that from the 20th, precisely on the summer solstice, a gradual rise in temperature will begin, more significant from the 21st and particularly in the maximum values, associated with a change in the atmospheric patterns", highlights the IPMA, in a statement.

This week, recalls the Institute, "we will be under the influence of a high-level depression approaching the northwest, which is associated with unstable and cloudy weather."

It "will be characterised by the occurrence of precipitation, temporarily intense and accompanied by thunderstorms, particularly in the North and Centre regions, and especially in the north of the Montejunto-Estrela mountain system until the end of the 19th, Wednesday".

But, from the 20th, "with the movement to the east of the aforementioned depression, an anticyclone will impose itself to the northeast of the Azores, gradually moving eastwards and cresting towards the Bay of Biscay, which together with a depression over the south of the Iberian Peninsula, will induce an easterly current and consequent gradual transport of dry air masses with tropical characteristics over mainland Portugal, which will be responsible for the rise in temperature values".

The IPMA highlights that "it is expected, with a high degree of confidence, that the regions with the highest maximum temperature values ​​are the interior of the South region, Beira Baixa and the Tagus valley, where values ​​should vary approximately between 36 and 38°C from the 23rd".