As hosepipe bans and fire warnings continue this week, a heat health alert will come into place across much of the country.

The UK Health Security Agency (UKHSA)’s amber alert covers southern and central England from midday on Tuesday until 6pm on Saturday, with experts advising people to look out for those who are older or with existing health conditions, as well as young children.

The Met Office has said that temperatures over the coming days will not reach as high as they did in July when the UK saw recording breaking temperatures of over 40C.

However, it is likely to reach the mid-30s in parts of the UK, and last much longer.

READ MORE: UK to face another heatwave ‘longer than July’s’ as 35C temperatures set to hit

Heatwave thresholds – which are met at different temperatures in different parts of the country – are likely to be hit in much of the UK.

UK Heatwave

Outside the hottest areas, much of England and Wales and south-east Scotland could see temperatures widely in the high 20s, with a chance of a few spots seeing temperatures into the low 30s, the Met Office said.

Scotland and Northern Ireland will also see temperatures in the high 20s and could reach official heatwave criteria by Friday, the forecasters said.

What is a heat health alert?

UK Health Security Agency (UKHSA) Heat Health Alert is an England-only service considering the impact of prolonged extreme heat on public health, especially for those with long-term health conditions.

What classes as a heatwave?

A heatwave is an extended period of hot weather, relative to the expected conditions of the area at that time of year.

The current temperatures far exceed those normally, therefore we are experiencing a heatwave.

The UK also has its own conditions to be met for a heatwave to be declared.

A UK heatwave threshold is met when a location records a period of at least three consecutive days with daily maximum temperatures meeting or exceeding the heatwave temperature threshold. The threshold varies by UK county.

What causes a heatwave?

Heatwaves are common in summer when high pressure develops across an area, the Met Office explains.

High pressure systems slowly move and can persist over many days or weeks. They can occur in the UK due to the location of the jet stream, which is usually to the north of the UK in the summer.

This can allow high pressure to develop over the UK resulting in persistent dry and settled weather.

With the latest heatwave coming after months of low rain, which have left the countryside and urban parks and gardens tinder-dry, households in some areas are being urged not to light fires or have barbecues.

The Met Office’s fire severity index (FSI), an assessment of how severe a fire could become if one were to start, is very high for most of England and Wales, and will reach “exceptional” for a swathe of England by the weekend.

Scientists warn that the likelihood of droughts occurring is becoming higher due to climate change, driven by greenhouse gas emissions from burning fossil fuels and other human activities.

Climate change is also making heatwaves more intense, frequent and likely – with last month’s record temperatures made at least 10 times more likely because of global warming, and “virtually impossible” without it, research shows.