Heatwaves in June more likely due to climate change

It's barely been a week since the first UK heatwave of 2025, but heat health alerts have come into force across most of England as the country braces for a second summer heatwave with temperatures expected to climb above 30C this weekend.

We're still only in the first month of summer, and generally our hottest weather usually occurs during July and August.

However, the statistics show that June heatwaves are becoming increasingly common and intense.

While some love the warmth, heatwaves can have huge consequences for us as a society, from adverse health impacts, to transport disruption and increasing the threat of wildfires.

June in the UK is typically the coolest of the three summer months, with average maximum temperatures of around 18C - that's around 2C below what we expect for July.

Things are changing though and a recent Met Office blog post points to "a clear upward trend" in the number of June days above 30C, external.

The increase varies for different parts of the UK, but according to the post "England consistently leads in the number of 30°C+ recordings, particularly in the south-east".

Climate scientists at World Weather Attribution (WWA) quantify how climate change influences the intensity and likelihood of extreme weather events.

They have found that the chance of seeing three consecutive June days above 28C in south-east England (the heatwave threshold for parts of the region) is now one in every five years.

During pre-industrial times south-east England only experienced these temperatures once every 50 years, meaning human induced climate change has made June heatwaves here 10 times more likely.

Recent years that have had significant June heatwaves include 2017 and 2020, and 2023 holds the title for the hottest June on record.

Whilst heatwaves in June are becoming more frequent, they are still not as intense as those in later in the summer, such as the record-breaking extreme heat of July 2022, when the UK recorded temperatures above 40C for the first time.

When intense heatwaves occur in the UK many people make comparisons with the extraordinary summer of 1976.

In June that year a very long-lasting heatwave developed and it still holds the record for the hottest June day ever recorded - a scorching 35.6C in Southampton.

However, when analysing historic weather data it is clear that 1976 was a significant outlier in an otherwise cooler decade.

During the entire decade of the 1970s for example, Heathrow recorded just 14 June days above 28C. Compare that with the current period, and since 2020 there have already been 26 days above 28C - and we're only halfway through this decade.

As our climate continues to warm what was once a rare meteorological event is now becoming a more regular feature of our early summers.

A dose of warm, sunny weather can really lift our mood but we can also reach a point of feeling too hot and uncomfortable and heatwaves can have serious health consequences.

How well our bodies deal with heat depends on several weather factors such as humidity, wind and cloud cover. It also varies hugely between individuals, with the elderly, the very young, those who are pregnant or people with underlying health conditions, particularly vulnerable.

The Office for National Statistics estimates that during 2022 there were more than 4500 excess deaths due to heat-related illnesses in England.

It's not just our health that is at risk, but also our natural environments, infrastructure and transport networks.

Network Rail estimates that in 2024 delays caused by rails that buckled due to extreme heat totalled 240 days.

Since 2021 the Met Office has introduced warnings for extreme heat, external which can be issued to alert the general public when temperatures are forecast to rise high enough and for long enough to cause significant disruption to our lives.

Lower level 'Heat Heat Alerts, external' are also issued by the UK Health Security Agency (UKHSA) that are aimed at emergency responders and professionals with the health and social care sectors.

Over the weekend we could see several parts of central and eastern England returning to heatwave conditions for three or more consecutive days.

Monday could be the hottest day of the year so far with a temperature of 34C, possibly 35C in London towards the Cambridgeshire area.

And, with Wimbledon starting on Monday, we could see the hottest ever start to The Championships, exceeding the previous opening-day record of 29.3C in 2001.

You can stay up to date with the temperatures where you are on the BBC Weather website and app.