PARIS — Europe’s record-breaking heat wave continues to wreak havoc on travel and transportation systems, including air service from one of the world’s busiest airports.

In Britain, travellers are facing a second day of disruption after soaring temperatures gave way to thunderstorms.

Network Rail, which oversees the majority of Britain’s railway network, is advising commuters to “only travel if their journey is absolutely necessary,” after Thursday’s disturbances left trains in haphazard locations and a fire damaged networks in the north.

The Met office says the mercury reached 38.1 C (100.6 F) in Cambridge on Thursday, only the second time temperatures over 100 F have ever been recorded in the UK.

The heat eased Friday, but Heathrow, Europe’s biggest airport, was forced to cancel or delay flights amid severe weather conditions. The airport admits they don’t know how many flights have been affected.

British Airways also announced that “severe thunderstorms are causing significant delays and cancellations to our operation in and out of London.”

In Paris, a power outage at Gare du Nord train station was disrupting travel Friday on the Eurostar to and from London and other routes around the region.

Eurostar urged passengers to avoid travel to or from Paris on Friday as workers fixed an overhead power line at the train station.

Two Eurostar trains have been cancelled and others are facing delays. Thalys trains that serve Brussels and Amsterdam are also seeing delays, along with domestic routes.

The power resumed Friday afternoon (local time) but the delays were expected to continue throughout the day, causing long lines in the London Eurostar terminal and on the Paris side.