An intense heatwave gripping Britain will peak today with what could be the hottest day in three years as an amber heat health alert was extended into tomorrow.

The Met Office said temperatures could hit 36C (97F) today after yesterday saw the hottest start to Wimbledon on record and a peak of 33.1C (91.6F) in London.

It comes after parts of southern England sweated through a tropical night which happens when temperatures stay above 20C (68F) overnight into the morning. 

Some tennis fans slept in the early heat after sunrise as they queued for day two of Wimbledon, with British number one Jack Draper and reigning women’s champion Barbora Krejcikova set to start their campaigns at the All England Club today. 

Commuters on the London Underground faced travel chaos this morning after a fire alert at South Kensington, which saw the Circle line completely suspended and the District and Hammersmith & City lines both part-suspended. A driver on one Tube train told passengers in an announcement that the fire was likely caused by the heat. 

Elsewhere, an emergency speed restriction was imposed from 10am to 7pm today between East Croydon in South London and Burgess Hill in West Sussex due to high track temperatures – affecting Gatwick Express, Southern and Thameslink trains.

If the mercury gets above 33.2C (91.8F) today it would make it the UK’s hottest day of the year so far – beating the current record set on June 21 in Charlwood, Surrey.

The heatwave will end after today, but conditions will remain warm – with 25C (77F) tomorrow, 26C (79F) on Thursday, 28C (82F) on Friday and 24C (75F) this weekend. 

The hottest day of 2024 was 34.8C (94.6F) in Cambridge on August 12; while the peak in 2023 was 33.5C (92.3F) in Kent on September 10; and the 2022 high was 40.3C (104.5F) on July 19 in Lincolnshire – the UK’s highest temperature on record.

The UK Health Security Agency (UKHSA) amber heat health alert warning of a ‘rise in deaths’ covers all of England apart from the North and will run until 9am tomorrow.

An official heatwave is recorded when areas reach a certain temperature for three days in a row, with thresholds varying from 25C (77F) to 28C (82F) in different areas.

Today, many parts of England will again pass above 30C (86F) as the heatwave continues, with 36C (97F) possible – while the rest of the UK will see more changeable conditions.

Met Office meteorologist Alex Burkill said there would be a ‘three-way split’ across the UK today, with high temperatures and ‘lots of sunshine on offer’ in south, central and eastern England.

He added: ‘There will be a bit of cloud here and there – you can’t even rule out one or two showers developing – but actually, across parts of the far South East, barely a cloud in the sky.

‘With all that sunshine, with all the hot weather that we’ve had recently, the heat’s going to continue to build (and) temperatures are going to rise a little bit higher.

‘Towards the South East many places high 20s (or) low 30s, but there’s potential that we could be looking at around 34, 35, maybe even 36C.’

Scattered showers coming from the South West will affect parts of Wales and northern England for a time today, while largely dry conditions are forecast across north-west Scotland and Northern Ireland, Mr Burkill added.

Fresher air is expected to sweep in from the continent over tonight into Wednesday, meaning it will start to feel ‘a bit more comfortable’ in many places, the forecaster said.

Amber heat health alerts issued by the UKHSA for Yorkshire and the Humber, the East Midlands, the West Midlands, the East of England, London, the South East and the South West were extended until 9am tomorrow.

A yellow heat health alert was also extended to the same time for the North West.

Health heat alerts are issued by the UKHSA and Met Office when weather conditions are expected to have severe impacts across health and social care services, including a rise in deaths, particularly among the over 65s and those with health conditions.

There are also concerns over an increase in demand on health and care services, and overheated hospitals and care homes.

The sweltering heat meant yesterday was one of the hottest June days ever, with UK temperatures for the month only surpassing 34C (93.2F) in only three years since 1960.

The hottest June day ever was 35.6C (96.1F), recorded on June 28, 1976.

Yesterday was provisionally the hottest start to Wimbledon on record, with 29.7C (85.5F) being recorded at the nearby Kew Gardens.

The previous record at the tennis championships – 29.3C (84.7F) – was set on June 25, 2001.

It marks the second heatwave for parts of the UK this month, with scientists warning searing temperatures of 32C (90F) earlier in June were made 100 times more likely because of human-caused climate change, while the heatwave that gripped south-east England was 10 times likelier.

They said heatwaves are becoming more frequent and intense due to climate change, and experts have warned heatwaves are ‘silent killers’, with the impacts of heat severely underestimated.

They also say that the UK is unprepared for the rising risk of extremely hot conditions that climate change is bringing – especially earlier in the summer, when people are less acclimatised to coping with it.

Professor Richard Allan, from the University of Reading, said the UK was on the edge of a ‘large dome of heat’ over continental Europe which was driving the heat wave, while ocean temperatures were also up to 2C above average to the south-west of the UK and ‘hotter still in the western Mediterranean’.

‘The ebb and flow of gigantic atmospheric waves have generated the stable, cloud-free conditions for heat to build up across western Europe,’ he said, but added that rising greenhouse gas levels due to human activities were making heat waves more intense.

Temperatures have climbed above 40C in countries including Italy, Spain and Greece, with holiday destinations such as Rome, Milan and Naples under the highest heat alert, while Greece is on high wildfire alert.

Dr Agostinho Sousa, head of extreme events and health protection at UKHSA, said: ‘The current spell of hot weather is forecast to continue until the middle of this week, with temperatures above 30C likely in most regions of England.

‘We are reminding everyone to take sensible precautions while enjoying the sun.

‘Remember that it is very important to check on friends, family and neighbours who are more vulnerable, as the temperatures we are likely to see over the next few days can result in serious health outcomes across the population, especially for older adults or those with pre-existing health conditions.’

Dr Friederike Otto, associate professor at Centre for Environmental Policy, Imperial College London, said climate change was an ‘absolute game-changer’ for heat in Europe, making heat waves more frequent and more intense.

‘Heat waves are called the silent killer, for a reason, every year thousands of people in Europe die due to extreme heat, particularly those that live in poorly insulated homes, on busy, polluted roads, and that already have health problems,’ she said.

‘But extreme heat also leads to agricultural losses, infrastructure failure and puts a big strain on plants and animals.’

Meanwhile, the Business Secretary has said the UK does not need additional workplace laws which would allow Britons to be sent home during hot weather.

Jonathan Reynolds said ‘behavioural changes’ like drinking plenty of water and staying protected in the sun were more important.

There is no law nor guidance in the UK for minimum or maximum acceptable workplace temperatures, but employers must follow health and safety law to keep temperatures at a reasonable level.

Mr Reynolds suggested a law change was not needed when asked if workers should be sent home in the event temperatures climb too high and there is no mitigation like air conditioning in place.

He said: ‘It is a hot day today for a northerner like myself. I’m struggling a little bit with it.

‘There are existing laws in place, the health and safety acts, around what a safe workplace should be. I don’t think we need more legislation in that area.’

He added: ‘Obviously, some behavioural changes, making sure people are hydrated, obviously are duly protected if they work, particularly outside.

‘I think we have got to make sure that we’re doing that. We shouldn’t need additional laws.’

Meanwhile, retailers warned today that fruit and vegetable prices in Britain have increased due to the hot and dry weather reducing harvest yields.

The British Retail Consortium (BRC) said this jump had contributed to shop prices having returned to inflation for the first time in almost a year.

Overall shop prices were 0.4 per cent higher in June than a year earlier – a significant jump from the decline of 0.1 per cent seen in May, according to the BRC-NIQ Shop Price Index.

Food inflation increased to 3.7 per cent from May’s 2.8 per cent in May, while fresh food was 3.2 per cent more expensive than a year ago.

Meat prices have also been hit by high wholesale prices and more expensive labour costs.