The UK is currently experiencing its fourth official heatwave of the summer, with extreme temperatures sweeping across large swaths of the country. After three earlier heatwaves, this new spell of intense heat has prompted both the Met Office and the UK Health Security Agency (UKHSA) to issue warnings and alerts to protect public health.
Heatwave Alert Details
On 11 August, the UKHSA issued a yellow heat-health alert for most of England—excluding the northeast and northwest. This alert ran from 12 pm Monday, 11 August, to 6 pm Wednesday, 13 August, signaling rising temperatures across the region.
By 12 August, the timing became more serious: certain areas—including the East Midlands, West Midlands, East of England, London, and the Southeast—were elevated to an amber heat-health alert, active from 9 am on Tuesday, 12 August, until 6 pm on Wednesday, 13 August.
On 13 August, with the heat unwavering, the yellow alert was extended to last from 6 pm that day to 6 pm on Monday, 18 August, covering more regions: Yorkshire and The Humber, East Midlands, West Midlands, East of England, London, Southeast, and Southwest. This shows how sustained and widespread the heatwave has become.
Record Temperatures and Heat Impact
During this heatwave’s peak, Northolt in London recorded a high of 33.4 °C on 12 August, matching the extreme heat felt across much of southern and eastern England. Temperatures of 33–34 °C were common in the southeast and Midlands. Some forecasts even expected highs up to 34 °C, particularly on Tuesday and Wednesday of that week.
Thunderstorm Warnings and Weather Shifts
As the heat persisted, conditions turned volatile. The Met Office issued yellow warnings for thunderstorms across parts of Scotland and Northern Ireland as summer’s fourth heatwave continued to dominate.
These warnings included the possibility of heavy showers, hail, and gusty winds, with rainfall potentially reaching 50 mm in some regions, disrupting roads, transport, and daily activities. For example, areas such as Aberdeenshire, Dundee, Edinburgh, East Lothian, and Glasgow faced warnings from 2 pm to midnight on Wednesday, while parts of Northern Ireland were also covered through Thursday evening.
Why It’s Called the Fourth Heatwave
The Met Office defines a heatwave as when temperatures exceed region‑specific thresholds for three consecutive days: 28 °C in London and the Home Counties, and 25 °C in cooler areas.
The summer of 2025 has now officially produced four such heatwaves:
- First heatwave: Mid‑June.
- Second heatwave: Late June to early July.
- Third heatwave: In July.
- Fourth heatwave: Starting 11 August and still ongoing.
This consistency of heat underscores a pattern of increasingly prolonged summers.
Health Risks and Public Safety
Heatwaves pose serious risks, particularly to the elderly, young children, and those with chronic illnesses. The UKHSA’s color-coded alerts are designed to guide vulnerable populations and institutions—such as care homes and hospitals—to take precautions.
Amber alerts indicate high health risks, including heat exhaustion, dehydration, and heatstroke, while yellow alerts signal moderate risk, urging awareness and preventative action.
Reports also reveal dramatic consequences:
- In past heatwaves, national heat-related deaths reached into the hundreds.
- Agricultural sectors face drought stress; wildfires have broken out, especially in rural and woodland areas.
- Medical services and transportation networks come under pressure during extended heat episodes.