Temperatures soared past 40 degrees Celsius (104 F) across parts of Europe over the weekend, as an early-summer heat wave tightened its grip on the continent.

In Spain, temperatures hit 46°C (114.8°F) on Sunday in the town of El Granado, near the Portuguese border, setting a new national heat record for the month of June.

The previous June high of 45.2°C (113.4°F) was set in Seville in 1965.

Temperatures above 40°C were also expected in neighboring Portugal, with the capital, Lisbon, under a "red warning" for heat until Monday night due to "persistently extremely high maximum temperature values," according to the Portuguese Institute for Sea and Atmosphere.

Extreme heat to reach London

In Italy, 21 cities, including Milan, Naples, Venice, Florence and Rome, were placed on high alert as extreme heat swept across the country.

Local authorities in Greece also issued fresh warnings about the risk of wildfires.

Hot weather is expected to persist into the start of the week, with London predicted to reach up to 35°C on Monday, marking the hottest day of the year so far. 

Wimbledon is set for its hottest opening day on record Monday, possibly breaking the tournament’s all-time heat record.

The current opening day high is 29.3°C, set in 2001. The hottest day ever at Wimbledon was 35.7°C on July 1, 2015.

The German Weather Service on Sunday issued heat warnings for southern and western regions, with peaks of 39°C expected on Wednesday.

Alerts were in place for the states of Baden-Württemberg, Bavaria, Hesse, North Rhine-Westphalia, Rhineland-Palatinate and Saarland.

French firefighters were battling early summer wildfires with several parts of the country under orange alert.

Blazes in the Corbieres region forced evacuations as temperatures soared past 40°C, peaking at 40.9°C in Grospierres.

Parts of the A61 motorway were closed, and a campsite in Bizanet was evacuated after a barbecue with smoldering embers in a trailer caused several fires, according to local civil protection authorities.

Birds impacted by heat

Meteorologists warn that heat waves are becoming more frequent and arriving earlier in the season due to human-driven climate change.

Spain's state weather agency, AEMET, noted that only two June heat waves were recorded between 1975 and 2000. That number has surged to nine since 2000. This year, temperatures typical of August arrived by late May.

"Heat waves will become more frequent and more intense," warned Emanuela Piervitali, a researcher at the Italian Institute for Environmental Protection and Research (ISPRA).

"A further increase in temperature and heat extremes is expected in the future, so we will have to get used to temperatures with peaks even higher than those we are experiencing now."

In France, experts warned the heat is taking a toll on biodiversity.

"Some nests reach over 40°C," said Allain Bougrain-Dubourg of the League for the Protection of Birds, adding that their care centers are overwhelmed with struggling birds.

Edited by: Darko Janjevic