British authorities announced a rare extreme heat emergency for large parts of England on Monday, with temperatures expected to exceed 40 degrees Celsius (104 degrees Fahrenheit) for the first time in British history.
The record-high temperatures were expected to disrupt travel, health care and schools as well as pose a serious threat to life.
Authorities placed more ambulances and medical workers on call amid health fears.
The Level 4 alert, issued by the Health Security Agency (UKSHA) for Monday and Tuesday, is defined as a "national heat emergency" and was triggered for the first time on record.
What kind of disruptions are expected?
The UK Met Office warned that the temperatures posed serious risks, including severe illness and death, even among healthy people.
It said there was a high risk of localized loss of power, water and mobile phone services.
The national rail network asked customers not to use its services unless essential.
Severe delays due to warped tracks and failing power supplies were expected, and some services, including a key route between northeastern England and London, were suspended for parts of Tuesday.
London's metro network was running a reduced service on Monday and Tuesday, urging commuters to only travel if absolutely necessary.
Luton airport near London had to suspend arrivals and departures of flights after the high temperature caused a defect on the surface of the runway.
While some schools were due to stay closed, others were preparing to cool off the children by setting up wading pools and water spray.
To relieve strain on the health service, some medical procedures were canceled.
What are the authorities advising?
With the British capital expected to endure the highest temperatures, Mayor Sadiq Khan issued a warning via Twitter, sharing the UKHSA's guidelines on how to cope with the heat.
It advises that Britons look out for others, especially those that are most vulnerable to the extreme weather. Hydrating frequently and staying indoors were also recommended.
As children and the elderly are among the most vulnerable to the impact of heat, nursing homes were urged to protect their inhabitants as well as possible.
Khan went on to discourage Londoners from using public transport and to be prepared for delays.
Cabinet Office Member Kit Malthouse said the government was prepared for the heat wave and would seek to learn lessons from it while British Prime Minister Boris Johnson was criticized for missing a meeting on Saturday concerning the government's response to the weather crisis.
Where else is the heat wave spreading?
The heat wave has been building over much of Europe's southwest, with wildfires raging in Portugal, Spain and France.
It was spreading north and was expected to reach Germany and the Netherlands by Tuesday.
The German meteorological service announced temperatures would climb as high as 40 C and would hit southwestern Germany the hardest.
Already on Monday, some 115 firefighters had to be deployed after a forest fire in the popular tourist destination of Saxon Switzerland in eastern Germany spread across an area of 2,500 square meters.
In France, more than 16,000 people, including both residents and tourists, were evacuated due to wildfires ravaging its tinder-dry forests in the southwestern region.
French authorities responded by setting up seven emergency shelters for evacuees.
They announced plans for more towns and 3,500 additional people at risk of falling victim to the fire to be evacuated.
According to local news reports, the country scrambled to send three extra water-bombing planes and a reinforcement of 200 firefighters to combat the spread of the wildfires on Monday, increasing the force of 1,500 firefighters in the southwest.
Several French towns recorded record temperatures on Monday, including the city of Nantes which saw the mercury hit 42 C, beating its previous record of 40.3 C set in 1949.
Spain managed to contain a wildfire that burned 2,000 hectares (5,000 acres) of woodlands in Andalusia, according to regional authorities. All 3,000 residents evacuated from the southern coastal city of Malaga were allowed to return to their homes, regional leader Juan Manuel Moreno said.
Spanish Prime Minister Pedro Sanchez said that "climate change is a killer" while visiting an area hit by fires in the region of Extremadura.
Wildfires in Portugal have killed two people and injured about 60 more. Between 12,000 and 15,000 hectares of land were burned in the hottest July on record after the country was hit with 47 C temperatures. Despite a slight drop in the heat level, most parts of the country remained on high alert for further wildfires.
Forecasters in Italy were expecting temperatures above 40 C in several regions in the coming days.
Switzerland also suffered the impact of the heat wave. The operator of a nuclear plant in Beznau stated that it reduced output to not overheat the plant as it relied on the river Aare to draw cooling water.
What is the cause for extreme weather events like this?
Climate scientists rarely attribute specific weather events to climate change, however, heat waves and extreme weather events become increasingly likely as global carbon emissions increase and global temperatures rise.
Studies show that the UK is now 10 times more likely to reach 40 C compared to the pre-industrial era.
Wildfires have also become more frequent and increasingly hard to fight due to climate change.
ab, los/nm (Reuters, dpa, AFP, AP)