The UK has recorded its hottest day of the year so far with a provisional temperature of 38.1C in southern England as Europe sweltered under a major heat dome.

As temperatures on the continent surpassed 40C at the peak of the summer's fifth heatwave, the thermometer at Kew Gardens in west London on Thursday surpassed the previous high of 38C on 28 June, the Met Office said.

In France, which has recorded 17 days of extreme heat – one of the longest periods ever – Bordeaux reached 39C and Nantes 37C, Paris was on 37C and Montpellier 35C. In Spain, a maximum of 42.4C was recorded at Miranda de Ebro, prompting fresh fears of wildfires in the two countries.

In the UK, Charlwood in Surrey recorded 37.1C, the second highest August maximum temperature since 2003. Teddington in London reached 36.1C, Pershore College in Worcestershire 36C, and temperatures in Wales reached 35C, according to provisional Met Office figures.

An amber extreme weather warning was issued on Thursday across east and south-east England, including London, the Midlands, north-west England, south-west England and parts of Yorkshire and Humber.

An extreme heat alert warning of significant impacts on health and social care services across the whole of England is in place until 9pm on Friday.

The Met Office has said this summer is on course to be the UK's hottest since records began, with 2026 likely to be the first year in which the country has recorded four separate days with temperatures of 36C or above.

Spain has broken its burned area record for this time of year, data published by the European forest fire information system on Thursday shows, while in France, the area burned had already by the third week of July surpassed that of any full year on record. Fire weather in the EU since the start of the year has been more severe than ever before.

The fires in many regions have been exacerbated by unusually dry conditions as heatwaves sap moisture from plants.

Firefighters in the UK continued to tackle a blaze in the New Forest in Hampshire. In the West Midlands, six homes were ablaze and two people were receiving treatment because of an extensive grassfire near Stourbridge golf course.

Across parts of eastern and southern Scotland, there were warnings about a very high risk of wildfires. With record dry conditions in July and a dry start to August, nearly three-quarters of England and the whole of Wales are in drought, heaping pressure on water resources for households, agriculture and the environment.

In mainland Europe, record-low water flows on the Danube have deprived thermal power plants of cooling water and forced some to reduce output as electricity demand for cooling grows. Romania on Thursday stopped the second of two reactors in its only nuclear power plant, which supplies about a fifth of the country's electricity. The plant's director told Agence France-Presse he did not foresee a restart within the next 10 days.

In neighbouring Hungary, one of a number of central European countries to break national heat records last week, engineers have resorted to laying stones to boost the water level of the Danube by the Paks nuclear power plant, which avoided a full shutdown in July but is producing only 25% of its usual output, up from 10% earlier this month. The prime minister, Péter Magyar, said work was proceeding at a rapid pace on Thursday.

The human-driven climate crisis is primarily the result of burning fossil fuels, which releases greenhouse gases that trap heat, raising temperatures. The extra heat alters the planet's water cycle and energy balance, making extreme events such as heatwaves, heavy downpours and severe drought significantly more frequent and intense.

People in the UK and Europe people have felt the effects of extreme heat throughout the summer. Julia King, the peer who chairs the adaptation work of the Climate Change Committee, an independent advisory body to the UK government, has said extreme weather "gets worse from here" until net zero is reached.

Doctors consider heat a "silent killer" because it greatly increases mortality rates while only occasionally being listed as the direct cause of death. In Germany, where meteorologists have issued heat warnings for a swathe of the west of the country for Friday, public health officials estimate that 12,500 people have died as a result of the heat so far this summer. More than 9,000 of these deaths occurred in an severely hot week in late June, when a national temperature record of 41.7C was set in eastern Brandenburg.

NHS staff working in A&E departments across England have experienced their busiest summer ever, health leaders said. The Royal College of Nursing said its members were working in inhumane conditions, "dripping with sweat from head to toe" during the record-breaking heat.

The RCN became the latest union to speak of unsafe working conditions for many members in hospital wards and care homes as the number of days of 30C-plus heat in the UK reached a record 35.

Extreme heat has driven a surge in attendance at A&E departments over the summer, with more than 2.4 million patients attending each month in May, June and July – the three highest monthly totals ever recorded.

The water industry regulator, Ofwat, said it would allow water companies in England and Wales to increase bills to spend £3.4bn more than planned to meet supply demands, including for the building of new homes and datacentres.

The Guardian has reported how Labour's target of building 1.5m homes by the end of this parliament has come up against the reality of water scarcity in many of the areas where most development is planned.