Heat health alert updated for London

Dear Colleagues,

This is an update to the exceptional spell of hot and humid weather which is expected this week.

High pressure will continue to dominate our weather this week, bringing plenty of fine, dry and sunny weather, with increasing temperatures and high humidity and very warm, tropical nights, where temperatures remain above 20 Celsius. There is a low risk of heavy showers/thunderstorms this evening although many places will remain dry.

Temperatures are expected to rise quickly this week. Temperatures will rise to high 20s today before rising to the mid-30s tomorrow and high 30s Celsius on Wednesday and Thursday, with high humidity levels. There is also a low risk of some areas potentially reaching 40 Celsius on Wednesday and Thursday. For context, the current UK June temperature record is 35.6 Celsius so it is highly likely we will break this, and the UK all-time high temperature record is 40.3 Celsius, which was set in July 2022.  

Given the exceptionally hot temperatures and high humidity that is expected, a RED Extreme Heat, HIGH likelihood of HIGH impacts Met Office National Severe Weather Warning has been issued for London, which is valid 09:00 Wednesday until 21:00 Thursday 25 June 2026.

Potential Impacts

• Population-wide adverse health effects experienced, not limited to those most vulnerable to extreme heat, leading to serious illness or danger to life
• Substantial changes in working practices and daily routines will be required
• High risk of failure of heat-sensitive systems and equipment, with the loss of power and other essential services, such as water, electricity, gas or mobile phone services
• Significantly more people visiting coastal areas, lakes and rivers, leading to an increased risk of water safety incidents
• Delays on roads and road closures, along with delays and cancellations to rail and air travel, with significant welfare issues for those who experience even moderate delays

Additionally, UKHSA has issued a RED Heat Health Alert for London. This is valid 01:00 Wednesday 24 June until 23:00 Thursday 25 June.

As a summary, the current weather warnings for London are as follows:

• AMBER, MEDIUM likelihood of MEDIUM impacts Extreme Heat warning valid now until 23:59 Tuesday 23 June;
• AMBER, MEDIUM likelihood of HIGH impacts Extreme Heat Warning valid from 00:00 Wednesday 24 June until 23:59 Thursday 25 June; and
• RED, Extreme Heat, High likelihood of High impacts Extreme Heat warning valid 09:00 Wednesday 24 June until 21:00 Thursday 25 June

The Daily Hazard Assessment also highlights Elevated to Severe Wildfire Conditions this week, with poor air quality, high to very high pollen levels and high UV Levels. The Flood Guidance Statement is currently green.

Please keep monitoring Hazard Manager, the Met Office App or Met Office website for the latest forecast and warnings. 

In addition, UKHSA have just issued an update on the Amber Heat Health alert and has increased this to RED (please see attached).

The red heat health alert is in effect from 1AM on Weds 24/06/2026 until 11PM on Thurs 25/06/2026 across London. The red alert has a matrix score of 16.

This means:

Severe impacts are expected across health and social care services due to the high temperatures, including:

• increased risk to life across the whole population, with significant impacts on older people
• significantly increased demand on all health and social care services
• the heat affecting the ability of the workforce to deliver services
• hot indoor environments making provision of care challenging and national critical infrastructure failures, such as generators and power outages
• water-related incidents may increase, including risks from cold-water shock and drowning

You can see all the weather health alerts currently in place across England on the UKHSA data dashboard.

Please ensure any local arrangements and actions are taken in line with the Severe Weather and Natural Hazards Framework  and local plans, and report any significant impacts in the usual way through your ICB, to the regional on call (NHS01).

Attachment:

• UKHSA RED heat health alert updated for London

Thank you

Kind regards,

Sent on behalf of the UK Health Security Agency (UKHSA)

The red heat health alert is in effect from 1AM on 24/06/2026 until 11PM on 25/06/2026 across London. The red alert has a matrix score of 16. This means:

Severe impacts are expected across health and social care services due to the high temperatures, including:

• increased risk to life across the whole population, with significant impacts on older people
• significantly increased demand on all health and social care services
• the heat affecting the ability of the workforce to deliver services
• hot indoor environments making provision of care challenging and national critical infrastructure failures, such as generators and power outages
• water-related incidents may increase, including risks from cold-water shock and drowning

You can see all the weather health alerts currently in place across England on the UKHSA data dashboard.

How to take action if you have a duty to respond

Please review the Weather Health Alert System user guidance to explain how you can use the information contained within the alerts to respond to the forecast weather.

We provide guidance on how to take action for a range of professional groups with a duty to respond, with action cards available for commissioners, health and social care providers, voluntary and community sector, and national government. Summary action cards are also available below:

·  commissioners

·  voluntary and community sector

·  care homes and other residential settings

·  services delivering care to people in their homes

·  hospitals and other healthcare settings

For an overview of the weather alerts in place across England, please check the UKHSA data dashboard.

The Met Office may issue National Severe Weather Warnings (for example, extreme heat) with short notice, so you can take appropriate action. Check the Met Office Website to see the National Severe Weather Warnings currently in place.

You can also find information of the latest weather forecast on the Met Office website.

How to protect yourself if you are vulnerable

While exposure to hot weather can affect anyone, some people are particularly at risk. We have published guidance on staying safe during hot weather.

Planning for adverse weather

All organisations should read the Adverse Weather and Health Plan. This is important if you provide health and social care. The plan explains what you should do before and while a heat health alert is in place.

To support local planning, please check the guidance on local resilience forums.

About heat health alerts

Chief executives of the following organisations in England receive heat health alerts:

·  health trust providers of NHS commissioned care

·  local authorities

·  social care organisations

The Heat-Health Alert Service in England runs from 1 June to 30 September each year, in partnership with the Met Office. This is the period when high temperatures are likely to occur.

If we observe high temperatures outside of this period, we will issue an extraordinary heat health alert. If this happens, stakeholders should take the usual public health actions.

You can share this email with your organisation or sign up to receive alerts using our registration form. We have a separate form if you would like to update your registration details.

Please let us know if you have a question or have a problem with your subscription. You can also unsubscribe from this service.

UKHSA and the Met Office use the Risk Matrix to assign a risk score for each alert. Users can refer the alert’s risk score to the matrix to understand the severity of the alert and likelihood of its impact.

Updates to heat health alerts

UKHSA and the Met Office make daily risk assessments. We will issue a new alert should the alert level change.

Further Advice and guidance

Flood Alerts and Warnings

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