The Met Office has issued a rare amber warning for extreme heat as Britain prepares for what could become one of the hottest June heatwaves on record, with temperatures forecast to climb as high as 38C and parts of Wales expected to experience their hottest weather of the year.

The warning, which now covers four days from Monday until Thursday, highlights the risk of widespread impacts on health, transport, infrastructure and essential services as an exceptionally hot and humid air mass spreads across much of England and Wales.

While the most intense heat will be felt across central and southern England, forecasters say Wales will also experience unusually high temperatures, with inland parts of south and east Wales expected to exceed 30C.

North Wales is forecast to become increasingly hot during the middle of the week, with temperatures widely reaching the high 20s and low 30s inland. Some forecasts suggest parts of North Wales could peak at around 34C on Wednesday or Thursday if the hottest air reaches the region.

The warning comes as a powerful area of high pressure draws exceptionally warm air northwards from continental Europe, where temperatures have already exceeded 40C in several countries.

Day-by-day forecast

Monday

The heat begins to build rapidly across England and Wales. Much of Wales will enjoy prolonged sunshine with temperatures climbing into the mid to high 20s. Inland areas of south Wales could reach around 30C, while North Wales is expected to see highs between 24C and 28C, with coastal areas remaining slightly cooler thanks to sea breezes. Humidity will also increase, making conditions feel more uncomfortable. (Sky News⁠)

Tuesday

The hot spell intensifies. Large parts of England are expected to exceed 34C, while Wales is likely to experience temperatures in the upper 20s to low 30s. North Wales could see inland temperatures around 28C to 31C. Warm overnight temperatures will provide little relief, particularly in towns and cities. (The Guardian⁠)

Wednesday

Forecast to be one of the hottest days of the week. Southern England could reach 38C, threatening the UK’s June temperature record. Inland areas of Wales are expected to exceed 30C, with North Wales potentially reaching around 32C to 34C if forecast models verify. Humidity will remain high, creating oppressive conditions and increasing the risk of heat-related illness. (The Telegraph⁠)

Thursday

Very hot weather is expected to continue across much of England and Wales before fresher Atlantic air gradually begins moving in from the west later in the day. Although temperatures may ease slightly in western coastal areas, inland parts of Wales and North Wales could still experience temperatures above 30C before conditions slowly become less extreme. (Sky News⁠)

The Met Office says the combination of high daytime temperatures, elevated humidity and unusually warm nights is what makes this event particularly significant.

In some towns and cities overnight temperatures may remain above 20C — known as a “tropical night” — making it difficult for buildings to cool down and increasing health risks for vulnerable people.

Health officials warn the greatest risks are to older people, babies and young children, those with existing medical conditions and anyone working outdoors. The heat can also affect healthy people, particularly during prolonged physical activity.

The Met Office says the heat could also lead to disruption across the transport network. Rail services may be forced to impose speed restrictions as tracks expand, road surfaces could soften, power demand is likely to increase as cooling systems work harder, and there is an increased risk of wildfires as vegetation becomes tinder dry.

Water safety experts are also urging people not to underestimate the dangers of rivers, lakes and reservoirs, where cold water shock remains a serious hazard despite the hot weather.

Although coastal communities in North Wales are likely to remain several degrees cooler than inland areas thanks to onshore breezes, forecasters say anyone travelling away from the coast should prepare for significantly hotter conditions than have been experienced so far this summer.

The heatwave is expected to ease later in the week as Atlantic weather systems return from the west, bringing lower temperatures and the possibility of showers or thunderstorms in some areas.