The Met Office has issued an amber warning for "extreme heat" in Hertfordshire this weekend.

The "exceptionally high temperatures" are expected to peak on Sunday, July 17 and Monday, July 18, with warm weather throughout much of England and Wales in the week.

The UK government's weather service has also warned of widespread impacts on both people and infrastructure.

The Met Office has warned of adverse health impacts "population-wide", not limited to the most vulnerable people. Health experts said this could lead to "potential serious illness or danger to life".

It is likely that "substantial" changes to working practices and daily routines will be needed, and there may be an increased risk of water safety incidents in lakes, rivers and the sea due to a higher number of visitors to coastal areas.

Road closures and delays are also possible, along with disruption to rail and air travel.

A Met Office spokesperson said: "Some exceptionally high temperatures are possible and cumulative effects of warm nights and hot days are expected to bring widespread impacts to people and infrastructure.

"This period of hot weather is expected to continue into the early part of next week, hence an update extending this warning into Monday is likely."

Dr Agostinho Sousa, of the UK's Health Security Agency, said: "Heat-health alerts have now been issued to the majority of the country, with temperatures set to remain consistently high throughout the duration of next week.

"Most of us can enjoy the hot weather when it arrives, but it is important to keep yourself hydrated and to find shade where possible.

"If you have vulnerable family, friends and neighbours, make sure they are aware of how they can keep themselves protected from the warm weather."

She also urged members of the public to check on elderly or vulnerable relatives and neighbours, and said passengers should not be left in stationery cars.

As of Monday, July 11, the Met Office forecasts highs of 24C in Hertfordshire on Friday, with a mix of cloud and sunshine.

Highs of 27C are expected in the county of Saturday, with temperatures in excess of 30C on Sunday.

As well as Hertfordshire, the amber warning covers London and the entirety of the East of England - including the neighbouring counties of Bedfordshire, Cambridgeshire and Essex.