Spain’s met office, Aemet, says the heatwave will likely last until at least Sunday, with temperatures potentially topping out at 44C.
The Foreign Office (FCO) has warned travellers to take extra precautions after the Spanish government issued health warnings.
South west Spain, including Madrid, parts of Extremadura and Andalucia, and the cities of Seville and Cordoba, have been placed on “orange alert”.
Said Aemet in a statement: “The spell will be particularly intense and long-lasting in the south west, the central area and the Ebro valley, with temperatures passing 40C from Wednesday.”
Britain’s own Met Office said travellers could expect “record breaking” inland temperatures in Spain, potentially as high as 48C, with some relief to be found in coastal areas.
Europe’s record temperature was 48C recorded in Athens in 1977. Temperatures reached 47.3C in Cordoba last year.
The rest of the Iberian peninsula is also affected, with Portugal bracing for 40C-plus temperatures too.
The FCO’s updated advice for travel to Spain reads: “The Spanish authorities are forecasting a sharp increase in temperatures over the next week.
“You can see the latest weather forecast on the Spain Met Office’s website. Please take care when out in the sun and consult the NaTHNaC website for advice on sun protection.
“High temperatures also carry an increased risk of forest fires; check on the outbreak of fires with the local civil protection authority.”