Each summer, as the UK warms under the sun, the dangers of heat are often overlooked. While floods and storms dominate headlines, heat waves quietly claim more lives than any other weather hazard. According to reports, heat-related deaths in the UK have more than tripled in recent years. Death rates have surged from 800 annually in the 2010s to over 2,800 in 2022.
In 2023, the UK Health Security Agency (UKHSA) and the Met Office developed a dedicated Heat Health Alert System to address this emerging threat. Unlike other general weather forecasts, this system focuses on the health impacts of extreme heat. It provides the public with timely and color-coded guidance to help save lives.
How the Alert System Works
The entire heat-alert system operates from 1 June to 30 September every year. It covers the summer months when heatwaves are most likely to occur. These alerts are based on different scientific criteria, not just on temperatures alone. There are five of them as follows:
- Forecasted maximum and minimum temperatures
- Relative humidity and effects like the urban heat island effect
- The ability of overnight temperatures to cool down
- Analysis of the overall projected pressure on local health services
- Population vulnerability and historic data
Alerts are updated daily and issued 24 to 72 hours in advance. It gives individuals and institutions ample time to prepare themselves for the upcoming heatwave.
🟩 Green Alert: No Immediate Concern
As the name indicates, a green alert is a baseline and refers to typical summer weather with no expected health impact. The temperature range is generally below 24°C in northern regions and around 26°C in southern ones. Therefore, the impact level in green alert is minimal as there are normal conditions.
Recommended actions for a green alert include staying hydrated, using sun protection, and enjoying the outdoors safely. This level can be understood as a reminder to maintain heat-aware habits, especially for people caring for the elderly or younger ones.
🟨 Yellow Alert: Vulnerability on the Rise
Yellow generally means caution, which signals an increased risk of health problems for vulnerable individuals. These individuals include seniors, infants, toddlers, and people with chronic conditions. The temperature range is typically between 27 and 30°C and lasts for at least two consecutive days.
Yellow alert indicates a 60% probability of exceeding region-specific heat thresholds. You should limit physical activity during peak heat hours, such as from 11 AM to 3 PM. Moreover, you should also keep rooms shaded and ventilated. Additionally, check on elderly neighbors or those living alone near you because they might need your attention.
🟧 Amber Alert: High Risk to Life
At the amber level, heat seriously threatens the entire population, not just vulnerable individuals. Typical conditions include prolonged periods above 30°C, often paired with high humidity and slight overnight cooling. Looking back at history, in 2022, Amber Alerts were linked to over 2,500 excess deaths in England alone.
Health system impacts include hospital advisories to prepare for an uptick in heat-related admissions. A recent example of an Amber Alert is the June 2025 heatwaves in England and Wales. In the wake of Amber Alert, avoid going outdoors unless essential, drink water frequently, and use cool baths or damp cloths for relief. You should also seek help if symptoms like nausea, confusion, or rapid heartbeat arise.
🟥 Red Alert: National Emergency
The red alert is rare but critical as it represents a nationwide health crisis. This is because the impacts of heat are severe and widespread. Red alerts are not issued normally, but during exceptional heat events like the July 2022 record of 40.3°C in Lincolnshire. You might face power outages and water shortages during this alert. Emergency services are stretched thin, while public transport and infrastructure disruptions can also be witnessed during these alerts.
Following a red alert, you should adhere to all official advice immediately. Move vulnerable individuals to cool yet safe environments and postpone outdoor activities and events. If convenient, use cooling centers.
What Should You Do at Each Level?
Here is a quick reference guide for taking action based on the alert:
- 🟩 Green: You should stay informed and practice sun safety
- 🟨 Yellow: It is advised to check on the vulnerable and reduce outdoor exposure
- 🟧 Amber: Staying indoors is highly recommended while getting hydrated and cooling your home
- 🟥 Red: It should be treated as an emergency. You should avoid all outside exposure
Final Thoughts: Know the Color, Save a Life
Heat-related deaths are often silent and preventable. Thus, the UK’s color-coded alert system turns invisible danger into visible action. Whether you are a student, a caregiver, or a city planner, understanding the meaning behind each alert is crucial, as it can help protect yourself and your community. When the next alert appears on your screen, don’t just check the weather but your readiness.
