An unusually early heatwave in drought-hit Spain is set to peak on Thursday and Friday with temperatures expected to break April records in the south of the country.

Since Monday, Spain has been enveloped by a mass of warm, dry air from North Africa that has driven up temperatures to "levels normally seen in summer and exceptionally high for this time of year," said Spain's state weather agency AEMET.

"It's highly likely (the heatwave) will peak on Thursday and Friday," it added, acknowledging many temperature records had already been beaten on Wednesday.

Scorching temperatures have prompted warnings about the "high risk" of wildfires in a nation that has already seen fire ravage 54,000 hectares (133,400 acres) of land so far this year, compared with 17,000 hectares in the same period last year.

Experts say parts of Spain are the driest in a thousand years, with a prolonged drought depleting reservoirs to half of their normal capacity, figures show.

On Thursday, the mercury was expected to rise above 34 degrees Celcius (93 degrees Fahrenheit) in most of the southern Andalusia region, hitting 37C in the Guadalquivir valley, it said after lowering earlier predictions of 40C.

On Wednesday, at least three areas around Seville and Huelva recorded temperatures of 37 Celcius.

The heatwave follows an abnormally warm and dry spring, spelling catastrophe for the agriculture sector in Spain, which is the world's biggest exporter of olive oil and a key source of Europe's fruit and veg.

The situation is so bad that some farmers have opted not to plant crops, with the COAG farmers' union warning that 60 percent of farmland was "suffocating" from lack of rainfall.

Madrid on Tuesday urged Brussels to activate the bloc's agriculture crisis reserve to help farmers cope with the exceptional drought, while also announcing a series of tax breaks.

Last year, Spain experienced its hottest year since began, with UN figures suggesting nearly 75 percent of its land is susceptible to desertification due to climate change.

Portugal was also feeling the heat with temperatures "10-15 degrees Celsius higher than normal" that could hit 37C on Thursday, the weather institute said, a day after the mercury touched 35.4 in the south.

© 2023 AFP