The maximum alert level (red) will be established in areas of Andalusia, Castilla y Leon, Castilla-La Mancha, Madrid and the Basque Country, according to forecasts by the specialized institution.
Temperatures are expected to begin to drop slightly on Thursday, but even so it will not be too noticeable. It is a stable extreme heat that adds to the arrival of warm, dry air from North Africa and dust in suspension.
The AEMET warning levels will be orange in Aragon, Asturias, Cantabria, Extremadura, Navarra and Rioja, while the range will be yellow in Catalonia, Galicia and the interior of the Valencian Community.
The agency said that probably the average temperature to be reached in Spain on Wednesday will be a record for the date since 1950.
Badajoz capital, with 44.8 degrees, had the primacy in thermometers according to statistics released by AEMET, followed by Merida (44.6 degrees) and Barcarrota (44 degrees), both also in the province of Badajoz.