Weekend heat builds towards peak early next week
Temperatures could reach the low 30s Celsius this weekend as a heatwave develops across parts of southern and south-east England, the Met Office has said. The official heatwave threshold is expected to be met for some areas over the weekend, with the warmth then set to “expand and intensify” at the start of next week, according to Greg Wolverson, deputy chief forecaster at the Met Office. He added that high temperatures overnight would lead to “potential impacts”.
Monday’s intensification
The Met Office has issued an Amber extreme heat warning for large parts of southern England and south-eastern Wales, effective from the start of next week. The peak of the heat is anticipated on Monday and Tuesday, with temperatures likely to reach 34°C, and a chance they could be exceeded. The highest recorded June temperature in the UK is 35.6°C, set in 1957 and 1976, and the Met Office estimates there is a 40 per cent chance of that record being broken next week.
The Amber heat warning covers much of southern England and parts of south-eastern Wales. In addition, the UK Health Security Agency (UKHSA) has issued Amber heat health alerts for London, the east, south-east and south-west of England, running until 8pm on Tuesday 23 June. Yellow heat health alerts are also in place for the Midlands. The heatwave is forecast to begin receding from the middle of next week, though southern and eastern areas may retain the warmth the longest.
High humidity is expected, making conditions feel close and more uncomfortable. “Tropical nights” — where temperatures do not drop below 20°C — are likely for some areas, reducing the body’s ability to recover overnight. The combination of heat and humidity also brings a risk of thunderstorms, particularly on Monday and Tuesday.
Potential impacts of prolonged high temperatures
The prolonged heat poses significant risks to health, infrastructure and water safety, according to the Met Office and UKHSA. The Amber extreme heat warning is designed to highlight these potential impacts to protect lives and property.
Health risks
The UKHSA has warned that vulnerable groups are most at risk. These include older people aged 65 and over, babies and young children aged five and under, pregnant women, and individuals with underlying health conditions such as heart, lung, kidney or mobility problems, dementia or diabetes. People on certain medications, those with serious mental health problems, people experiencing homelessness, and those living alone or in top-floor flats with limited ventilation are also particularly vulnerable.
Extreme heat is linked to an increase in deaths, especially among older age groups. The five heat episodes in 2022 caused nearly 3,000 excess deaths in England and Wales, and projections suggest heat-related deaths could triple by 2050 without adaptation measures. Hot weather can worsen cardiovascular and respiratory diseases, kidney disease and electrolyte imbalances. Higher temperatures are also associated with negative impacts on mental health, including increased suicide risk and hospitalisations for psychiatric conditions. The “tropical nights” expected next week can exacerbate health impacts by depriving people of a chance to cool down overnight.
Elevated temperatures can also worsen air pollution, increasing concentrations of ozone and particulate matter, which further affects respiratory and cardiovascular health.
Water safety
The Met Office has flagged water safety as a particular concern, as more people are likely to visit coastal areas, lakes or rivers to cool off. Cold water shock remains a danger even in warmer weather. The Royal National Lifeboat Institution (RNLI) advises entering open water slowly to acclimatise and to “float to live” if in danger. The Met Office app features a dedicated beach forecast with tide times, wave heights and sea-surface temperatures, along with water safety advice.
Infrastructure and transport
Extreme heat can disrupt transport systems, affecting staff and passengers and threatening safety and reliability. Rail tracks may buckle, road surfaces can melt — prompting the deployment of gritters — and speed restrictions on rail lines are likely. Services such as the London Underground may face issues with air conditioning. The electricity grid can also be compromised, with power lines operating at reduced efficiency and potentially sagging, while increased demand for air conditioning strains the network. Extreme heat and drought can lead to soil shrinkage and cracking, causing subsidence and degradation on roads and other infrastructure.
Wildfires
Hot and dry conditions increase the risk of grass fires and wildfires. Records have been broken for the amount of UK land burnt by wildfires during hot periods.
Climate change context
Heatwaves are becoming more frequent, longer and more intense globally and in the UK due to climate change, the Met Office has said. The UK experienced record-breaking temperatures in July 2022, exceeding 40°C for the first time. Projections indicate that hot spells will become more frequent, particularly in the south-east, and that summers as warm as 2018 could occur about 50 per cent of the time by mid-century. The 1976 heatwave remains the longest official heatwave in the UK, lasting 15 consecutive days, while the 2003 heatwave was the most severe single event in recent times, with significant health effects across Europe.
Government and health response
The UKHSA and Met Office issue heat health alerts (Yellow and Amber) to warn of potential health impacts. The Adverse Weather and Health Plan, published in April 2023, is the overarching policy for heat response in the UK, replacing the previous Heatwave Plan for England. It includes an impact-based heat health alert system. The National Adaptation Programme outlines government responses to climate change impacts, focusing on overheating in buildings and calling for more research into heat risk. Public health advice includes staying hydrated, keeping cool, planning activities for cooler times of the day, and checking on vulnerable individuals.
The Met Office has also warned that the heat and humidity bring a risk of thunderstorms on Monday and Tuesday, which could bring localised disruption.
