The UK Health Security Agency (UKHSA) has set out how its Weather-Health Alert system works, confirming that the system was updated in June 2023. Previously, alerts were triggered when temperatures reached a specific threshold; the revised system takes what the agency describes as a more sophisticated approach1.
The agency says the alerts are issued after a joint risk assessment with the Met Office when periods of particularly hot or cold weather are forecast. The factors now considered are temperature thresholds informed by impacts on health observed in previous years, how long the weather event is expected to last, how many regions are affected, the potential for conditions to escalate, compounding risks such as snow, ice, wind or flooding, and whether the system is already under strain for other reasons, such as hospitals already experiencing high demand1. UKHSA says the change reflects the latest evidence on how temperature affects mortality, observed impacts on the health and social care system during recent heatwaves, and long-term weather trends across England's regions1.
The alert levels are set out as follows1:
| Level | Meaning |
|---|---|
| green (preparedness) | No alert is issued as the conditions are likely to have minimal impact on health; business as usual; summer or winter planning and preparedness activities |
| yellow (response) | Alerts covering a range of situations; may be issued during periods of heat or cold unlikely to impact most people but which could impact those who are particularly vulnerable |
| amber (enhanced response) | Weather impacts likely to be felt across the whole health service, with potential for the whole population to be at risk; non-health sectors may also start to observe impacts and a more significant coordinated response may be required |
| red (emergency response) | Significant risk to life for even the healthy population |
UKHSA states that the alerts are primarily aimed at the health and social care sector and emergency responders, although they may be of interest to a wider audience1. The agency draws a distinction with the Met Office's National Severe Weather Warning Service, which covers a broader range of weather hazards such as flooding or storms for a wider audience across the UK. A key difference, it says, is that UKHSA's system includes yellow alerts, while the Met Office's Extreme Heat warnings begin at amber. UKHSA adds that the two systems have slightly different audiences and aims, and that it may issue amber before the Met Office does, with the two organisations in constant contact during alerting and warning periods1.
"UKHSA's yellow alerts focus on people who are particularly vulnerable - such as older adults and those with certain long-term health conditions. At this level, action is essential within health and social care settings."
Cold temperatures are handled separately through Cold-Health Alerts, which UKHSA assesses alongside other factors as part of a dynamic risk assessment conducted with the Met Office. The Met Office does not issue cold temperature-specific warnings as part of the National Severe Weather Warning Service, publishing instead warnings for high-impact conditions including rain, fog, wind, thunderstorms, snow and ice1. For high temperatures, England has two early warning systems: Heat-Health Alerts issued by UKHSA and Extreme Heat warnings issued by the Met Office. A slightly different threshold is used to trigger Heat-Health Alerts in London because of generally higher temperatures there1.
Why it matters for households
Weather-Health Alerts cover England only, because this is a devolved responsibility in Scotland, Wales and Northern Ireland1. The automated alerting system allows users to specify which area of England they want updates about, and UKHSA says people can register for alerts, view current alert status on its Data Dashboard, or follow its social media accounts1. The agency says that during a Weather-Health Alert it reminds the public to check on friends and family who may be vulnerable due to age or health conditions1. It also notes that a cold snap posing little risk to most of the population can be dangerous for older adults or people with heart conditions, and that a heatwave which does not meet the threshold for a national weather warning may still require urgent action in hospitals and care homes1.
What happens next
No further changes to the system have been announced. UKHSA says it and the Met Office carry out a joint risk assessment when periods of particularly hot or cold weather are forecast and issue alerts where necessary, and remain in close contact throughout winter so that Cold-Health Alerts are issued as early as possible1. Current alert status is published on the UKHSA Data Dashboard, and current UK weather warnings on the Met Office website1.
Households can read more on The UK Health Security Agency: Alerts, Outbreak Advice and Local Teams, on what each level means in Heat-Health Alerts: Yellow, Amber and Red Explained and Yellow, Amber and Red Cold-Health Alerts: What They Mean, and on registering in How to Sign Up for Heat-Health Alerts.
UK Health Security Agency
Heat-Health Alerts Explained
Signing Up for Heat Alerts
