(Bloomberg) -- Temperatures in Spain will reach unusually high levels for this time of the year amid a heat wave that’s expected to take thermometers above 40 degrees Celsius (104 Fahrenheit) in some parts of the country.

The heat wave, caused by a mass of hot and dry air coming from North Africa, will reach its peak between Friday and Saturday, Spain’s meteorological agency Aemet said on Tuesday. Temperatures in some parts of Morocco also will hit  40°C this week, according to the country’s weather agency.

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“It’s really extreme, we’re talking about temperatures 10 to almost 20 degrees Celsius above the average for May in some places,” said Francisco Doblas-Reyes, a researcher based in Barcelona and a contributor to the United Nations’ latest Intergovernmental Panel on Climate Change report. “It’s not just the intensity, but the duration of it, too.”

The heat wave adds to a long list of extreme weather events in recent weeks that show the impact of climate change. Dangerous temperatures have hit the south and central U.S. this month, while a separate heat wave is impacting India and Pakistan. Such events have become more frequent and will persist as the planet warms, according to the latest assessment by UN-backed scientists.

Maximum temperatures in parts of Spain could reach 42°C, the agency said; the lows also will be higher than usual, dropping to 24°C in some places. France is also set to experience higher-than-average heat for this time of the year, said Doblas-Reyes, who heads the Earth Sciences Department at the Barcelona Supercomputing Center and is a professor at the government-backed ICREA foundation.

“The frequency and intensity of heat waves will happen in places that are already hot, but will be worse in areas with a milder climate because they’re not adapted to extreme events,” he said. “In areas of central Europe where buildings are not adapted to heat, for example, vulnerable people will be at risk.”

The heat wave comes at a critical time for agriculture, as many crops are heading to harvest season, Doblas-Reyes said. The extreme events could compromise ecosystems and the availability of water following a relatively benign and dry winter in most of Spain.

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