MADRID (AP) — As parts of Spain set record temperatures during a heatwave, U.K. residents were sweltering Friday on what was expected to be the country's hottest day this year.

San Sebastian on Spain's northern coast witnessed 42 degrees Celsius (107 degrees Fahrenheit) on Thursday -- the hottest temperature there since records began in 1955, the national weather agency said.

The city of Palma, on Spain's Mediterranean island of Mallorca, set a local record of 40.6 degrees Celsius (105 degrees Fahrenheit) on Tuesday.

The Spanish weather agency, Aemet, said tropical nights— when temperatures do not fall below 20 degrees Celsius (68 degrees Fahrenheit) — were also frequent in many parts of Spain in July.

“Climate change is increasing the frequency of heatwaves,” it said, adding that the annual number of days in heatwave conditions has doubled since the 1980s.

To the north, the Met Office, Britain's official forecaster, said temperatures could reach 36 degrees Celsius (96 degrees Fahrenheit) in some areas Friday, especially in the east and southeast of the country. It warned of thunderstorms.

The U.K. hot spell was not expected to last, however, as a weather front moving in from the west was forecast to lower temperatures on Saturday.