LONDON: Travelers faced a second day of travel disruptions in Britain on Friday after a heat wave gave way to thunderstorms, and technical problems at the air traffic control center grounded many flights at the country’s two main airports on one of the busiest days of the year.

A day after the country potentially recorded its hottest day ever, travelers at London’s Heathrow and Gatwick airports faced delays after the UK’s air traffic controller, NATS, said it had identified a technical problem that was causing flight restrictions.

It was not clear if the matter was related to the hot weather or the ensuing thunderstorms.

“We are doing all we can to fix it as soon as possible,” NATS said in a statement.

Eurocontrol, the European air traffic body, said the technical problem is being caused by an “issue with radar displays” and hefty delays are expected for flights arriving at Heathrow and Gatwick for the rest of Friday.

This weekend is a big travel moment as families head off for their summer holidays now that schools have broken up for the academic year.

Britain, along with much of Western Europe, endured one of its hottest days ever on Thursday, potentially its hottest. The country’s weather service said a provisional temperature of 38.7 degrees Celsius (101.7 degrees Fahrenheit) was recorded at Cambridge University Botanic Garden in eastern England, which if confirmed would be the highest ever recorded in the UK.

The existing record for the UK is 38.5 Celsius (101.3 Fahrenheit), was set in August 2003.

It said “quality control and analysis over the next few days” will determine whether the reading becomes official.

Rail commuters were also facing delays after the heat wave prompted Network Rail to impose speed restrictions in case the tracks buckled. Engineers from the company have been working to get the network back to normal after the track temperatures soared to up to 20 C (68 F) more than the air temperature.

“With the railway being made of metal and moving parts, the sustained high temperatures took their toll in places,” said Phil James of Network Rail. “Everything was done to keep trains moving where possible, and last night hundreds of staff were out fixing the damage and repairing the railway ready for today.”

Passengers using Eurostar services to and from Paris were also facing “severe disruption” due to overhead power line problems in the French capital, which on Thursday recorded its hottest day ever with the temperature rising to 42.6 C (108.7 F).

Authorities across Europe were looking to address the consequences of Thursday’s soaring temperatures, as records that had stood — in some cases for decades — fell.

Europeans and tourists alike jumped into fountains, lakes, rivers or the sea to escape a suffocating heat wave rising up from the Sahara. Britain, France, Belgium, Germany, the Netherlands — all places where air conditioning is not typically installed in homes, cafes or stores — strained under the heat.

In France, Interior Minister Christophe Castaner linked the country’s 60 drowning deaths so far this month indirectly to the current heat wave, warning that drownings are up 30% this month compared to last July.

Castaner noted a rise in people drowning in unguarded bodies of water as they seek relief from high temperatures, some of whom suffer thermal shock when they jump from hot air into cold water.

In Belgium, a 66-year-old woman died near her caravan close to the beach.

The woman was found by a neighbor late Thursday afternoon after she had apparently been basking in the blazing sun. The incident happened in Middelkerke on the Belgian coast as temperatures rose in the region to over 40 degrees Celsius. (104 Fahrenheit)

Middelkerke police commissioner Frank Delva told The Associated Press that the death is “very clearly linked to the heat.”

Emergency services rushed to the scene but could not resuscitate the woman.