How does the new Met Office heatwave alert system work?

London is set to experience its hottest day of the year on Saturday with 29C temperatures and a thunderstorm forecast.

Health authorities have issued the first heat-health alert of 2023 with the UK Health Security Agency and the Met Office is saying the alert would apply for 72 hours from 9am on Friday.

Authorities have said it will apply to London, the East Midlands, West Midlands, East of England, the South East and the South West. Those aged over 65 and with health conditions have been warned.

The warning comes following the launch of a new alert initiative, aimed at helping people cope with heatwaves which could hit the UK more frequently in the coming years.

Known as the Weather-Health Alerting system, it will issue warnings to people when summer temperatures reach dangerous levels.

The launch followed a warning from the Met Office that future heatwaves could be “more intense and last longer” than they currently do.

The UK had, at the time of writing, its hottest day of the year so far on May 30, with temperatures reaching 25C in parts of the country.

Here’s everything you need to know about the Weather-Health Alerting system.

How does the Weather-Health Alerting system work?

The Weather-Health Alerting system, introduced by the UK Health Security Agency (UKHSA) and the Met Office, sends information and advice when severe heatwaves have been forecast. The Manchester Evening News said the initiative had been launched to reduce deaths within at-risk groups.

The publication says the scheme will issue four types of coloured alerts. These range from green, which means there is no risk to health, to red, which will indicate a “significant risk to life for even the healthy population”.

The initiative replaces the Met Office’s Heat-Health Alerts and Cold Weather Alerts system, which finished on June 1.

What do different colour warnings mean?

There are four levels of warning: Green, yellow, amber and red.

Green is no alert.

Yellow flags that some response is needed and will be issued when the heat or cold could have some impact on the health of a vulnerable person. Although the chances of this could be unlikely.

Amber is for when local authorities and the NHS should set up a response for a weather event which is likely to have some impact on the whole country.

Red, the most serious, means there is a significant risk to life - even for the healthiest. All sectors would be asked to organise a coordinated response.

Who will use the new Weather-Health Alerting system?

The government, commissioners and health and social care professionals will use the system to prepare them for when a “breakdown in public services” could be expected.

It will issue forecasts for five days, six to 15 days, and 16 to 30 days ahead.

For more information on the scheme, visit this website.

To sign up for the alerts, click here.

When was the UK’s last heatwave?

The Met Office said the UK experienced a brief but unprecedented extreme heatwave over July 16-19, 2022. The weather body said this came as hot air moved north from mainland Europe, with extreme temperatures recorded on both July 18 and 19.

On July 19, 40.3C was recorded at Coningsby in Lincolnshire. This set the UK and England temperature record by a margin of 1.6C, while multiple stations across England also exceeded 40C.

This heatwave was a milestone in UK climate history, with 40C being recorded for the first time.

The Manchester Evening News reported that the UKHSA said 2,803 people aged 65 and over died during five “heat periods” across England last summer. The deaths marked the highest number on record since 2004.

Dr Agostinho Sousa, head of extreme events and health protection at the UKHSA, told the Manchester Evening News: “Last year saw record high temperatures across England and evidence shows that heatwaves are likely to occur more often, be more intense and last longer in the years and decades ahead.

“It is important we are able to quantify the likely impacts of these heatwaves before they arrive to prevent illness and reduce the number of deaths.”

A government spokesperson added: “The Government and emergency services are well prepared for any future heatwaves.

“Since last summer’s hot weather, we have worked across Government to identify and implement lessons.

“This included the publication of the UK Health Security Agency’s Adverse Weather and Health Plan, which contains guidance on extreme heat and outlines how everyone can work together to respond to heatwaves.”