The Met Office has issued an amber weather warning for extreme heat across a large part of the UK next weekend as temperatures on Monday reached 32C and rail services were disrupted. The alert, starting from Sunday 17 July, came as sales of fans, ice-cream, sun lotion and parasols soared in the heatwave. The Met Office said temperatures in the south-east could exceed 35C (95F) this weekend, posing a potential risk to life. “Population-wide adverse health effects are likely to be experienced, not limited to those most vulnerable to extreme heat, leading to potential serious illness or danger to life,” the forecaster said. “Substantial changes in working practices and daily routines [are] likely to be required. Significantly more people are likely to visit coastal areas, lakes and rivers, leading to increased risk of water safety incidents.” It added: “Delays on roads and road closures are possible, along with delays and cancellations to rail and air travel, with potential for significant welfare issues for those who experience even moderate delays.” The warning is being enforced for the whole of Sunday across the east Midlands, east of England, London, south-east, north-east, north-west, south-west, Wales, West Midlands and Yorkshire and Humber. The forecaster added it could be extended to Monday. On Monday railway lines at Battersea Bridge, in south-west London, were closed on Monday after a fire broke out at rush hour. A Network Rail spokesperson said a wooden beam was alight and the cause of the fire was under investigation. West Midlands Trains also said Network Rail had imposed a 20mph speed restriction between Kidderminster and Stratford-upon-Avon from 11am until 8pm owing to the sweltering conditions. A Network Rail spokesperson said: “With extremely hot temperatures expected this week, our specialist weather teams will be monitoring key hotspot locations to make sure we can keep services running safely and reliably for passengers. “Speed restrictions are likely to be in place in some parts of the network most affected by the hot weather. This helps because slower trains exert less force on the track and reduce the likelihood of buckling, avoiding the major disruption caused by a buckled rail.” Elsewhere, fire services have urged people to have picnics instead of barbecues during the warm weather after a spate of grass fires. Hampshire county council said it was preparing to deploy gritters to protect cars against melting roads. Temperatures reached 32C in Northolt, west London, at about 3pm on Monday but did not surpass the UK’s record high for this year, which stands at 32.7C, taken at Heathrow on 17 June. The TUC released a video on Twitter, saying that “no one should work in temperatures above 30 degrees”. John Lewis said it had sold 1,633% more parasols, 471% more fans, 525% more air conditioning units and 193% more blackout curtains in the last week. Waitrose reported a 250% week-on-week increase in sales of fans. Waitrose said it had sold 220% more sun cream, 55% more sausages, 45% more kebabs and 20% more ice-cream as some made the most of the hot weather. It also reported a 188% increase in searches for canned cocktails on its website. Searches for barbecues increased by 133%, it added. Sainsbury’s said it expected a 500% increase in ice-cream sales by the middle of this week. The Met Office forecaster Dan Stroud said it was possible – though not likely – that temperatures could reach 40C at the weekend. The highest recorded UK temperature was 38.7C in Cambridge in July 2019. Stroud said: “To be honest there is probably about a 30% chance of that being surpassed next Sunday or Monday.” The Met Office and the UK Health Security Agency (UKHSA) issued a level 3 heat health alert from 9am on Monday to 9am on Friday in the east and south-east of England, with the rest of the nation having a level 2 alert in place.