LONDON — Train shuttle services between Britain and France were hit by the heat wave on Friday, with passengers warned to expect delays, air-conditioning issues and to stock up on water before boarding.

“It’s a very busy day, it’s the day when everyone leaves on holiday,” said a spokesman for Eurotunnel, which operates a drive-on train service for cars and trucks passing through the Channel Tunnel.

The tunnel runs for 50 kmbetween Kent in southeast England and northern France. Opened in 1994, it is the world’s longest uninterrupted undersea link.

“The high temperatures are affecting the operation of air conditioning on our trains resulting (in) delays. We recommend you stock up with drinking water before you arrive,” Eurotunnel said on its Twitter account.

On Thursday, Eurotunnel delays hit four to five hours. At the British end of the tunnel, the company said there was now a 30-minute delay pre check-in plus a two-hour wait on site.

On the domestic rail network, passengers were urged to avoid traveling on the main line running up the east coast of the country between London and Edinburgh after lightning damaged the signaling system.

Train firm Northern advised passengers not to travel in Yorkshire, northern England, due to the same issue.

Meanwhile motorists were warned ahead of lightning, flash flooding and large hailstones, with a thunderstorm warning in place through the rest of Friday.

The hottest temperatures of the year in Britain were recorded on Thursday. The mercury hit 35.1 degrees Celsius (95.2 degrees Farenheit) in Wisley on the southwest edge of London.

Will Lang, chief meteorologist at the Met Office national weather service, said Friday: “The heat wave conditions are coming to an end but it’s another hot day in the east and southeast of England today with temperature expected to reach 36C (96.8F) or 37C (98.6F) in places. — AFP