Spain faces an intense heatwave this week as temperatures across the southern regions are set to surge toward 40 C, prompting an official weather alert.

The State Meteorological Agency, or AEMET, warned on Sunday of "full summer heat" arriving from Wednesday, driven by high-pressure systems and a mass of hot, dry air settling over the Iberian Peninsula.

The predicted temperatures, running more than 10 C above seasonal averages, raise fresh concerns about water shortages in a country that has faced recurring heatwaves in recent years, reported The Guardian newspaper.

The forecast echoes conditions from May 2022, when parts of Spain recorded their highest temperatures for the month, suggesting a pattern of increasingly early summer heat.

In a statement, AEMET said there would be "progressively higher temperatures in the Iberian Peninsula and the Balearic Islands" this week.

Ruben del Campo, a spokesperson for the agency, said: "The last week of May will see a high-temperature episode across a good part of the peninsula, with the kind of temperatures normally seen in high summer, especially from Wednesday.

"In some southern parts of the peninsula, we could see maximum temperatures of more than 40 C, and the temperature won't drop below 20 C in that region or in Mediterranean areas."

AEMET said the hottest regions will be the southeast, the central region, and the Ebro Valley in the north, with temperatures set to reach 35 C in central and northern areas and up to 40 C in the southern region of Andalucia by Thursday.

The heat is forecast to last until Saturday, when clouds and dust could bring cooler conditions.

"We're talking about maximum temperatures that are between 5 and 10 degrees above normal for this time of year," said del Campo.

The AEMET statement explained that the cause of the change in weather is the presence of a powerful anticyclone centered in the Azores and extending across the Iberian Peninsula and the Balearic Islands, resulting in very stable weather, virtually clear skies, and high levels of sunshine.

Spain's highest ever temperature was recorded in August 2021, when readings in the Andalucian town of Montoro, near Cordoba, reached 47.4 C.

A 2022 AEMET analysis showed that the annual arrival of 30 C temperatures across Spain and the Balearic Islands had moved an average of 20 to 40 days earlier in the year during the past 71 years.

"The summer is eating up the spring," del Campo told the El Pais newspaper at the time. "What's happening fits perfectly with a situation where you have a warmer planet."

He added that the rise in temperatures was a "direct and palpable (consequence) of climate change ... The climate in Spain isn't the one we used to know. It's got more extreme."