Heat-Health Alerts: Yellow, Amber and Red Explained

A heat-health alert is an official warning that forecast hot weather is likely to affect people's health. The alerts are issued by the UK Health Security Agency (UKHSA) in partnership with the Met Office, and they cover England only¹. They come in three colours, yellow, amber and red, each describing how far the expected impacts reach: yellow means the heat could harm people who are particularly vulnerable, amber means impacts are likely across the whole health service with the potential for the whole population to be at risk, and red means a significant risk to life even for healthy people².

For an ordinary household, an alert is a signal to act before the heat arrives: keep cool, drink enough water, check on anyone at higher risk, and look after babies and young children. The alerts are issued by the UK Health Security Agency in partnership with the Met Office³. You can check the current status at any time on the UKHSA Data Dashboard⁴, and you can register to have alerts sent to you by email¹.

What a heat-health alert means for your household

A heat-health alert is not a weather forecast in the usual sense. It is an early warning, issued when adverse temperatures are likely to affect the health and wellbeing of the population, giving you and the services around you time to take precautions⁶. The system exists to give early warning to the health and social care sector, the responder community, the voluntary sector and government departments, but the alerts are also aimed at the public, and for individuals they provide situational awareness that health and wellbeing may be at risk, allowing precautions to be taken⁵.

The Heat-Health Alerts are part of a wider Weather-Health Alerting system that also issues Cold-Health Alerts in winter, and the whole system underpins the government's Adverse Weather and Health Plan, which sets out how services respond when weather threatens health⁵. So when a yellow alert lands in your inbox, hospitals, care homes and community groups in your region are receiving the same signal and preparing their own responses. Your part is the household side of the same effort.

In practice, an alert tells you three things: that hot weather is forecast in your region, that it is expected to affect health, and roughly how serious those effects could be. What it does not do is tell you the weather itself in detail, so you still need the forecast. Somerset Council's advice captures what a household should actually do when an alert is in force: stay hydrated, avoid the hottest part of the day, keep indoor spaces cool where possible, and check on vulnerable people⁹. Our pages on keeping your home cool, who is most at risk and heat exhaustion and heatstroke cover each of those in depth.

One point of possible confusion: a "heat alarm" in your kitchen is something entirely different. A heat alarm is a warning device that detects an increase in temperature from a fire but is insensitive to smoke, and it has nothing to do with heat-health alerts¹⁰. If you have heard the phrase "heat alert" in the context of home fire safety, that is the device on the ceiling, not the email from UKHSA.

The four alert levels: green, yellow, amber and red

The system has four levels, and the colours describe the response expected, not just the temperature outside. Green is the baseline state during the season: no alert is issued because conditions are likely to have minimal impact on health, though organisations are still expected to have plans in place¹. Above that sit the three alerting colours, each given based on the combination of the impact the weather conditions could have and the likelihood of those impacts being realised¹¹.

The same four-colour structure is used by the Cold-Health Alert service in winter, so once you understand one, you understand both¹². The levels are cumulative in spirit: everything you would do at yellow still applies at amber and red, with more urgency and wider scope.

Since 2023, the Heat-Health Alerts have used impact-based alerting, meaning the colour reflects the expected effects on health and services rather than simply whether a temperature threshold has been crossed¹. That is why two heatwaves with similar forecast temperatures can carry different alert colours: what matters is who is expected to be harmed and how likely that is.

Yellow alerts: warnings about risks to vulnerable people

Yellow is the alert level most households will actually see, and it is the one most easily misread. A yellow alert does not mean the heat is dangerous for everyone. It may be issued during periods of heat that would be unlikely to impact most people, but could impact those who are particularly vulnerable⁵. It is also used when forecasters have low confidence that conditions may lead to more significant impacts, so a yellow alert can sometimes be an early, uncertain signal of something worse².

Who counts as particularly vulnerable matters here. Official guidance now describes older people as those aged 65 years and over, a change from the previous guidance of 75 years and above¹³. Older people, and people with heart, respiratory and other serious health problems, are the groups most vulnerable when the temperature starts to rise¹⁴. The Welsh Ambulance Service adds young children and babies, and those with a heart or respiratory condition such as asthma, to the list of people to check on¹⁵, and the Scottish Ambulance Service gives the same advice to check on family, friends and neighbours who may be at higher risk of becoming unwell, and, if you are at higher risk yourself, to ask them to do the same for you¹⁶.

A real example shows how a yellow alert looks in practice. In August 2026 a yellow heat-health alert was issued for the South West region, running from 9am on Tuesday 12 August until 6pm on Wednesday 13 August¹⁷. Note the two features: it named a specific region, and it gave exact start and end times. That is the standard shape of an alert, and it tells you precisely when to be careful and when normal service resumes.

For a household, a yellow alert is the moment to do the simple things. The voluntary and community sector action card for yellow alerts advises ensuring sufficient cold water and ice are available to minimise risks from dehydration¹⁸, advice that translates directly to your own kitchen. Check on older neighbours and relatives, keep babies and young children out of the sun, and follow the basics of sun safety, including wearing sunscreen¹⁹. If you want a structured approach, our hot weather preparation checklist covers what to have ready before the season starts.

Amber and red: when heat affects everyone and services

Amber is where the alert stops being mainly about vulnerable people and starts being about the population and the health system. An amber alert indicates that weather impacts are likely to be felt across the whole health service, with potential for the whole population to be at risk, and that other sectors apart from health may also start to observe impacts, indicating that a coordinated response is required². In some circumstances, the Met Office may issue an Extreme Heat warning under its National Severe Weather Warning Service in conjunction with, and aligned to, the Weather-Health Alert, indicating significant impacts are expected across multiple sectors¹².

For your household, amber means two things at once. First, take the heat seriously for yourself and everyone in the home, not just the most vulnerable members, because the whole population is potentially at risk. Second, expect pressure on services: an amber alert signals likely increased demand on health and social care services, as the Met Office noted when Heat Health Alerts were issued alongside an amber Extreme Heat warning in 2026²⁰. Plan around that: do not leave getting help to the last moment, and know the signs of heat exhaustion and heatstroke and when to call 999 or NHS 111.

Red is the highest level and the rarest. A red alert indicates significant risk to life for even the healthy population². At this level, central government will declare an emergency in the event of severe or prolonged hot weather affecting sectors other than health and requiring a coordinated multi-agency response¹⁸. A red heat-health alert is a national event, and you should expect it to lead the news, with instructions to follow from official channels. At this level the expected impacts are population-wide adverse health effects, not limited to those most vulnerable, leading to serious illness or danger to life².

The action card for the voluntary and community sector gives a sense of the scale of response expected at the upper levels: during yellow and amber alerts, and at red, organisations are told to monitor temperatures regularly during the hottest periods in all areas where patients or clients reside, and to ensure designated cool areas are below 26°C¹⁸. That figure is a useful benchmark for your own home too: if a room someone vulnerable is resting in cannot be kept below 26°C, moving them somewhere cooler, or to a cool space in the community, is the kind of step the alert system is prompting.

How alerts are decided: forecast temperatures, impact and likelihood

Alerts are not triggered by a single national temperature. The Met Office regional daytime and night-time maximum temperature forecasts are monitored, and when certain temperature thresholds are reached, an assessment is made of the potential impacts and their likelihood¹. The thresholds themselves are regional, which is part of why alerts name a region: the temperature that matters in the South East is not the same as the one that matters in the North East. Our page on what counts as a heatwave in the UK explains the regional threshold system in detail.

The process behind an alert runs like this. UKHSA and the Met Office monitor the weather forecasts, and where episodes of hot or cold weather are identified using predefined evidence-based considerations, a joint dynamic risk assessment is carried out and the appropriate alert issued³. When periods of particularly hot or cold weather are forecast, the two organisations carry out a joint risk assessment and issue alerts when the criteria are met²¹. The colour is then set by the combination of two things: the impact the weather conditions could have, and the likelihood of those impacts being realised¹¹.

That two-part test explains the otherwise puzzling cases. A very hot forecast with uncertain impacts can come out as yellow, because the likelihood is low. A slightly less hot forecast with high confidence in serious impacts can come out higher. Surrey County Council describes the system as four levels of response based upon temperature thresholds reached and an assessment of impact by UKHSA and the Met Office²², which captures both halves: the temperature observation and the judgement about what it will do to people.

The Weather-Health Alert system as a whole is operational year-round²³, but within it the heat alerts have their own season, and the system also produces heat-health planners: within the core alerting period, heat-health planners are issued every Monday and Friday to provide a weather-health outlook². Planners are the forward view that services watch between alerts, and registered users receive them too.

The alert season: 1 June to 30 September, and alerts outside it

The core Heat-Health Alert season runs from 1 June to 30 September each year³. That is when the system is in full operation, with alerts and the Monday and Friday planners flowing to everyone registered. The service has been in operation since 2004, and it is designed to help healthcare professionals manage through periods of extreme temperature¹.

One document gives a different end date: Surrey County Council states the annual Heat-Health alert system in England operates from 1 June to 15 September²², while UKHSA's own guidance and user guide give 1 June to 30 September³.

Heat does not always respect the calendar. Should an episode of heat occur outside the core period, an extraordinary alert will be issued². The same applies on the cold side of the system: an out-of-season alert may still be issued if impacts from adverse weather on health, heat or cold, are expected³. So a genuinely hot spell in May or October can still produce an alert, but it will be labelled as extraordinary rather than part of the routine season. If you are registered for alerts, you will receive those too; there is no separate sign-up.

How to sign up for heat-health alerts by email

Alerts are distributed by email to all those who have registered to receive them once they are issued²⁵. Registration is free and open to individuals as well as organisations: individuals can register to receive the alerts via an online form¹, and when you register you can specify which regions you wish to receive alerts for²³, so you only hear about the parts of England that matter to you.

The Greater London Authority sets out who the service is really for at household level: if you, or someone you care for, is at higher risk, you can sign up for the UK Health Security Agency's Weather-Health Alert service, which will notify you by email if forecast temperatures are likely to have an impact on health. You can also sign up on behalf of someone who does not have an email account or who finds it difficult to access information online²⁶. That last point is worth acting on: registering on behalf of an older relative who never checks email, and passing the alerts on by phone or in person, is one of the most useful things a neighbour or family member can do. Our page on how to sign up for heat-health alerts walks through the form step by step.

If you would rather not register, you can still see the current status. The alert status is publicly available on the UKHSA Data Dashboard²³, which shows the heat-health alert level for each region and is updated regularly; on 18 August 2026, for example, the dashboard showed no alert in force as of 09:00am⁴, with the South East page reading "No alert" and describing little impact observed on health, healthcare services and social care provision, business as usual²⁷. Somerset Council also directs people to the Met Office for the latest information about heat alerts⁹.

Who the alerts are written for, and why the colours rarely reach the news

The Heat-Health Alert service is aimed at health and social care professionals and anyone with a role in reducing the harm extended periods of hot weather can have on health¹. The Local Government Association is blunter still: the content of these alerts is aimed at health and social care organisations and other professionals that work with individuals or communities who may be affected by hot or cold weather⁸. The Heat-Health Alerts target the health and social care sector and the responder community, while the Met Office's warning service has a wider audience²³.

This is why the alert colours rarely lead the news. The impact-based alerts, the colours themselves, are not typically used in public-facing communications²³. The public hears about hot weather through Met Office forecasts and warnings, through the general advice to keep cool, and through local messaging, rather than through a newsreader announcing that UKHSA has raised the region to amber. For a household, that means the surest way to know your region's alert level is to be registered for it or to check the dashboard yourself, rather than waiting for it to reach you second-hand.

There is a recognised gap here. A government report on public messaging for summer concurrent risks, published in December 2025, found that most advice in the reviewed documents was provided in English only, with very limited multilingual accessibility, and that there is limited evidence of content designed for people with different literacy levels, languages or cultural contexts²⁸. If someone in your household or street struggles with English-only official advice, passing on alert information yourself is not just helpful, it is filling a gap the official system has acknowledged.

Heat-health alerts and Met Office weather warnings: what is different

UKHSA's Weather-Health Alerts are separate from the Met Office's National Severe Weather Warning Service²¹. The two systems look similar, with colours doing similar work, but they weigh different things. The Weather-Health Alerts are weighted on adverse effects to public health and healthcare capacity¹², while the Met Office warnings cover the wider impacts of severe weather, from transport to infrastructure. The health alert service was previously issued by the Met Office and is now issued by UKHSA's own online alerting system, but remains in association with the Met Office for weather forecast input¹².

The two systems are designed to work together rather than compete. Since summer 2021, UKHSA and the Met Office have collaborated to ensure that the Heat-Health Alerts and Extreme Heat warnings are aligned and work together to communicate the expected impacts so that users act to minimise the potential impact²³. One practical difference in the colours: the Heat-Health Alert system will issue yellow to red alerts, whereas the Met Office issues only amber and red alerts for Extreme Heat²³. So a yellow heat-health alert with no Met Office warning alongside it is a normal, coherent situation: the heat is expected to affect vulnerable people's health, but not to threaten the wider infrastructure the Met Office warns about.

For a household, the simplest rule is to treat the two as complementary. The Met Office warning tells you the weather is severe; the heat-health alert tells you whose health is at risk and what services are doing about it. In a heat episode with both in force, follow both.

Cold-health alerts in winter

The same system runs a mirror image in the cold months. The Weather-Health Alerting System is made up of the Heat-Health Alerts and the Cold-Health Alerts⁵, and the Cold-Health Alert service has four colour states, like the Heat-Health Alert¹². Cold-Health Alerts are issued when cold weather is forecast that could lead to significant impacts on health, and the system provides suggested actions to protect health and reduce cold-related harms²⁹. The core cold alerting season runs from 1 November to 31 March each year⁵, and during that period cold-health planners are issued every Monday and Friday²⁹, exactly as the heat planners are in summer.

The colours work the same way: alerts are given a colour, yellow, amber or red, based on the combination of the impact the weather conditions could have and the likelihood of those impacts being realised³¹. Official statistics on cold mortality monitoring describe the levels as yellow (response), amber (enhanced response) or red (emergency response)³², the same response ladder as the heat side.

The actions the alerts prompt are the cold-weather equivalents of checking on neighbours in a heatwave. For a yellow cold alert, the advice includes monitoring temperature in places where vulnerable individuals spend substantial time; for an amber alert, actively monitoring high-risk individuals during cold weather episodes, checking that those most vulnerable to cold-related illnesses have visitor or phone call arrangements in place; and for a red alert, considering daily visits or phone calls to those vulnerable to cold-related illnesses³¹. As with heat, extraordinary alerts may be issued if an episode of cold that can impact health occurs outside the core period²⁹, and a cold-health alert may still be issued out of season if adverse weather is expected³⁰.

The Weather-Health Alerting System is made up of the Heat-Health Alerts and the Cold-Health Alerts together³³. Educational settings can also sign up to receive Weather-Health Alerts from UKHSA and the Met Office, and these alerts underpin the Adverse Weather and Health Plan³³. For the household side of winter readiness, our storms, snow and ice guide and the heating and cooking without mains power guide cover what to have ready when the cold alerts start arriving.

A short history of the alert service

The heat-health alert service has been in operation since 2004, and it was designed to help healthcare professionals manage through periods of extreme temperature¹. For most of its life it worked on temperature thresholds alone: alerts fired when regional forecast temperatures crossed defined lines. In summer 2023, the Heat-Health Alerts transitioned to impact-based alerting, which provides users with information on the impacts expected rather than just the temperatures forecast¹, and since 2023 the alerts have given professionals information on the impacts of hot weather².

The Weather-Health Alerting system brought the Heat-Health Alerts and the Cold-Health Alerts together, and it is provided by the UK Health Security Agency in partnership with the Met Office⁸. From 1 June 2024, Heat-Health Alerts and Heat-Health Planners have been issued by UKHSA in collaboration with the Met Office²³. The direction of travel is clear: from a simple temperature trigger for hospitals, towards a year-round, impact-based early warning system that households can plug into directly by email.