Authorities in the UK have asked parents to keep their children indoors as the temperatures are set to soar above 33°C on Tuesday.

Sheffield Children's NHS Foundation Trust has advised parents against letting their children run around in the sun and has asked them to keep them hydrated to avoid any mishap.

"Don't allow your children to stay in the sun for long periods – and never leave them in a car on a hot day. Resting in the shade and finding cool places is important," read a statement by the trust on Twitter.

"The first sign that a child is overheating is when they become grumpy or complain of a headache. If this happens, get them into a shaded place that is as cool as possible. Remove any clothing you can, give them water to drink and get them to rest," it added.

The warning comes as the country experiences extremely hot days that may prove deadly. The Met Office has, in fact, issued a level three heat health alert from Monday to Friday next week.

A level two alert has also been issued for the southwest, east Midlands, west Midlands, the northwest, Yorkshire and the Humber regions, according to a report in The Independent.

According to the Met Office, the highest temperatures could reach 33°C on Tuesday, although temperatures will also be widely above average through next week.

"The warm weather over much of England and Wales could last for much of next week," said David Oliver, the Met Office's deputy chief meteorologist in an advisory last week. He added that much of this week will remain warm and the effects will be seen in southern and central areas of the country.

The national weather service also said that the higher concentration of carbon dioxide in the environment has led to an increase in the frequency of heatwaves. These have become more likely to occur every year due to climate change.

Globally, the decade to 2019 was the hottest recorded, and the five hottest years have all occurred within the last five years.

Britain flooded by visitors
The authorities have asked parents to keep their children indoors. Photo: AFP / Glyn KIRK