BritainThe first red warning of extreme heat has been issued as temperatures It is forecast to rise to 40C on Monday and Tuesday.
Ministers held state of emergency Cobra meeting on Saturday amid predictions that the record for warmest day will be broken.
The Met Office’s highest alert, meaning life-threatening, has been issued in London, Manchester and York, among others.
TfL chief Andy Lord has now warned customers to travel alone if their journey is essential.
He told LBC: “We advise all our customers to travel alone if their travel is essential, to ensure they stay hydrated and have water with them when they need to travel.
“Check them before they travel, because travel times are extended. We have fewer services over the TFL network due to the security restrictions we have to put in place due to the heat. ”
He outlined what the safety restrictions were and added: “Especially on the railways, such as National Rail, we had to introduce speed limits.
“If the track temperature rises above 50C, we need to reduce the speed to reduce the risk of track damage. In extreme cases, the rails can buckle, which we must prevent and maintain the safety of the railway.”
Meanwhile, the UK Health Security Agency has issued its “national emergency” level four heat warning to medical and healthcare organizations.
It said illness and death can occur among the “fit and healthy”.
London North Eastern Railway has urged people not to travel on Tuesday.
“DO NOT TRAVEL between #LondonKingsCross and south of #York & #Leeds on Tuesday 19th July as there will be no trains,” reads a tweet.
“Travel to other destinations only if necessary.”
People who have already purchased tickets are urged to visit the LNER website for information on refunds.
The chair of the NHS Confederation has said hospitals will be “really, really pushed” in the coming days.
Lord Victor Adebowale said the NHS will “compete” in the coming days, but added “combat is not good enough”.
He told Times Radio: “My members are pretty stretched right now. Ambulances are running at their peak, waiting times for ambulances are now getting longer.
“We’re going to get really, really pushed and it’s not just the red alert, the heat wave. We are dealing with Covid which is causing illness in our ambulance crews and that is one of the reasons we have vacancies. And we also have a challenge for social care, which is that we can’t get people out of the hospital because social care is on its knees.”
Lord Adebowale added: “The NHS will be able to handle it, but dealing with it is not good enough. We need to work so that people get the treatment they need, wherever they are needed, on time. And that is a struggle.”