UK weather: What is the heat-health alert issued by the Met Office and who is most vulnerable?

A heat-health alert has been issued as forecasters say we could be in for the hottest day of the year this week.

A yellow alert is in place for the whole of England, apart from the North East.

The alert, issued by the UK Health Security Agency (UKHSA) and the Met Office, is in place until 9pm on 10 September.

But what does it mean - and who is most at risk during hot weather? Sky News explains.

What is a heat-health alert?

It is issued during periods when there are high temperatures which may affect public health.

It currently only applies in England and is aimed at "health and social care professionals and any with a role in reducing the harm extended periods of hot weather can have on health."

The alert is provided by the UKHSA in partnership with the Met Office from June to September and has been in operation since 2004.

Information included in the alert aims to give users detail "over and above the fact that hot weather is likely to occur".

Dr Agostinho Sousa, from the UKHSA, said the hot weather will "primarily" impact people over the age of 65 or "those with pre-existing health conditions such as respiratory and cardiovascular diseases".

The UKHSA has also advised people to be "aware" of the temperatures and to check on friends, family or neighbours that are more vulnerable.

What are the different types of alerts?

The Met Office has said the "regional daytime and night-time maximum temperature forecasts are monitored and when certain temperature thresholds are reached the Met Office and UKHSA undertake an assessment of the potential impacts and likelihood of those impacts occurring."

A decision is then made on whether an alert is needed.

Here are the different alerts:

Green - summer preparedness

An alert is not issued during these conditions as it is likely to have minimal impact on health.

However, the Met Office has warned that it is still important for organisations to ensure that it has a plan in place should an alert move to yellow, amber or red.

Yellow - response

Yellow warning alerts cover a range of situations.

It may be issued during periods of heat which would mainly impact people who are vulnerable - such as elderly people with health conditions.

"A yellow alert may also be issued if the confidence in the weather forecast is low, but there could be more significant impacts if the worst-case scenario is realised," the Met Office website has said.

In this case, the alert may then be upgraded as the weather and impacts improve.

During a yellow warning, people can still continue with their daily routine, but there may be some minor impacts such as travel disruptions.

Amber - enhanced response

An amber alert is issued when a situation is likely to impact the whole health service, with the potential for the whole population to be at risk.

The Met Office has said that at this point, "a coordinated response is required."

In some circumstances, a National Severe Weather Warning Service (NSWWS) Extreme Heat warning may be issued in conjunction with and aligned with the HHA.

An amber warning may cause travel delays, rail closures and a potential risk to lives and properties.

Red - emergency response

This is the most significant and dangerous warning.

A red alert would indicate that there is a huge risk to life across the population.

This warning would be issued and aligned with a red NSWWS Extreme Heat warning.

If a red warning is put out, people are advised to take action in order to stay safe.

There may be disruption to travel, energy supplies, damage to property and risk of life.

If a warning like this is announced, the Met Office has said people should "avoid travelling, where possible, and follow the advice of the emergency services and local authorities."

Who is the most vulnerable during hot weather conditions?

According to the NHS, a heatwave can affect anyone, but the most vulnerable people are:

• Elderly people, especially those over the age of 75.

• People who live on their own or in a care home.

• People who have a serious or long-term illness including heart or lung conditions. Illnesses also include kidney disease, Parkinson's disease or diabetes.

• Those who might find it hard to keep cool. This includes babies as well as those who may be bed bound.

• If you spend a lot of time outside or in hot places, you might also be at risk.

Read more:
What is a 'heat dome' and how long will hot spell last?
How to sleep better when it's hot

The impact of hot weather conditions

Whilst many like to enjoy the sun, the Met Office has said it is important to remain cautious in order to stay safe, as overexposure to the sun can be harmful.

"Hot weather places a strain on the heart and lungs. For that reason, the majority of serious illness and deaths caused by heat are respiratory and cardiovascular. Older people, those with pre-existing health conditions and young children are particularly at risk," it added.

Overexposure to the sun is also dangerous, with its effects ranging from mild sunburn to skin cancer.

Hot weather can also impact places such as water supplies, energy utilities, road and rail transport and health and fire services.

What is the weather forecast for this weekend?

You can check the weather forecast for your area by putting your postcode in here.