What is the difference between Weather-Health Alerts and Severe Weather Warnings? – UK Health Security Agency

During summer and winter, UKHSA and the Met Office monitor weather forecasts to help health and social care professionals, emergency responders, the voluntary sector and the public prepare for adverse conditions. When periods of particularly hot or cold weather are forecast, we carry out a joint risk assessment and issue alerts where necessary.

UKHSA’s Weather-Health Alerts (WHAs) are separate from the Met Office’s National Severe Weather Warning Service (NSWWS) – and understanding the difference matters.

Weather-Health Alerts focus specifically on the health impacts of weather. They are primarily aimed at the health and social care sector and emergency responders, although they may be of interest to a wider audience. During a WHA, we remind the public to check on friends and family who may be vulnerable due to age or health conditions.

The National Severe Weather Warning Service covers a broader range of weather hazards such as flooding or storms for a wider audience across the UK.

A key difference is that UKHSA’s system includes yellow alerts, while the Met Office’s Extreme Heat warnings begin at amber. 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.

The 2 systems have slightly different audiences and aims, and therefore we may issue amber before Met Office do, but that we are in constant contact during alerting/warning periods to ensure there is a shared picture of the weather situation

What do the different colours of Weather-Health Alert mean?

• 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) – these alerts cover a range of situations; yellow alerts may be issued during periods of heat or cold that would be unlikely to impact most people but could impact those who are particularly vulnerable
• amber (enhanced response) – 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; non‑health sectors may also start to observe impacts and a more significant coordinated response may be required
• red (emergency response) – a red alert indicates significant risk to life for even the healthy population

What triggers a Weather-Health Alert?

UKHSA’s Weather-Health Alert system was updated in June 2023. Previously, alerts were triggered when temperatures reached a specific threshold. The new system takes a more sophisticated approach, considering:

• temperature thresholds (informed by impacts on health we have 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
• if the system is already under strain for other reasons, such as hospitals already experiencing high demand

This 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 regions.

Cold-Health Alerts

The Met Office does not issue cold temperature-specific warnings as part of the NSWWS. Instead, it publishes warnings for high-impact weather conditions including rain, fog, wind, thunderstorms, snow and ice.

UKHSA takes a different approach. We consider cold temperatures explicitly through our Cold-Health Alerts, assessing them alongside other factors as part of a dynamic risk assessment conducted with the Met Office.

UKHSA and the Met Office remain in close contact throughout winter to ensure Cold-Health Alerts are issued as early as possible. Met Office warnings contribute to decisions about alert levels.

Heat-Health Alerts

England has 2 early warning systems for high temperatures:

• Heat-Health Alerts (HHAs) issued by UKHSA
• Extreme Heat warnings issued by the Met Office as part of the NSWWS

Due to generally higher temperatures in London, a slightly different threshold is used to trigger Heat-Health Alerts in that region.

Why do UKHSA’s Weather-Health Alerts only cover England?

The Met Office’s National Severe Weather Warning Service covers the whole of the UK. Weather-Health Alerts cover England only due to this being a devolved responsibility in Scotland, Wales and Northern Ireland. The automated alerting system for Weather Health allows users to specify which area of England they want to receive updates about.

How can I receive notifications?

You can register for Weather-Health Alerts here or visit our Data Dashboard to view current alert status across England. We also share alerts on our social media accounts.

You can check current UK weather warnings on the Met Office website.

Weather affects different people in different ways. A cold snap that poses little risk to most of the population can be dangerous for older adults or people with heart conditions. A heatwave that doesn’t meet the threshold for a national weather warning may still require urgent action in hospitals and care homes. By maintaining a dedicated Weather-Health Alert system alongside the Met Office’s National Severe Weather Warning Service, we ensure that health and social care professionals receive targeted, actionable guidance – while the public continues to benefit from broader weather warnings. Both systems work together to protect lives.