An amber weather warning for extreme heat early next week has been issued for West Wales as meteorologists upgrade warnings for some parts of the UK to red.

The extremely rare red weather warning will cover a large swathe of the midlands, with west Wales sitting under an amber warning for extreme heat from Monday until the end of Tuesday.

The mercury is set to hit over 31C in places such as Tenby and surround areas on Monday with the Met Office warning the extreme heat is likely to bring widespread impacts to people and infrastructure.

The Met Office, who have issued the amber warning from midnight Monday until the end of Tuesday, said: “After a very warm night, hot weather, already underway across other parts of England and Wales is expected to develop more widely across Wales, southwest and northern England, plus southern Scotland.

“Some exceptionally high temperatures are possible, both by day and by night, for Monday and Tuesday.

“This following a warm weekend, will likely bring widespread impacts to people and infrastructure.”

Elsewhere in the country, those living in the red warning zone could see record-breaking temperatures.

The Met Office added: “Exceptional, perhaps record-breaking, temperatures are likely on Monday, then again on Tuesday. Nights are also likely to be exceptionally warm for the UK, especially in urban areas.

“This is likely to lead to widespread impacts on people and infrastructure. Temperatures are expected to drop away from Wednesday onwards.”

Deputy Chief Medical Officer for Wales, Chris Jones said: “Extreme heat warnings are not issued lightly by the Met Office and the potential health risks need to be taken seriously.

“Very high temperatures can be dangerous for everyone but elderly people, children, those with chronic health problems and vulnerable people who may struggle to keep cool are at a higher risk.

“Demand on NHS Wales and our emergency services is already high so by taking extra precautions to keep ourselves and our families safe, we can all help to reduce pressure on these vital services.

“These temperatures can be particularly worrying for vulnerable or elderly people so I would also urge people to check in on neighbours and relatives to make sure they are keeping as cool as possible as the temperature rises.”

The extreme heat warning coincides with the start of the Royal Welsh Show in Llanelwedd.

Visitors and exhibitors should follow all advice from the show organisers to ensure the safety and well-being of attendees and welfare of animals.

Anyone who owns or is responsible for an animal has a legal duty to take reasonable steps to ensure its welfare needs are met. Show exhibitors should inspect their animals often.

If they have any concerns about the welfare of livestock, they should immediately contact the on-site veterinary team.

Welsh Government Ministers and officials are also taking part in UK-wide Civil Contingencies structures to ensure a co-ordinated approach to cross-border issues caused by the extreme heat.

Transport for Wales (TfW) and Network Rail are asking customers to check before they travel on public transport with hot weather likely to cause disruption and affect travelling conditions.

With the Met Office issuing a rare amber warning for extreme heat, conditions will be challenging for travel by both rail and road, with temperatures expected to reach the mid-thirties in Wales by Monday.

Temporary Speed Restrictions are likely to be in place across the rail network to reduce the risk posed by overheating rails. This will likely increase journey times and lead to short-notice alterations to services.

Extreme temperatures could also lead to other infrastructure and fleet challenges such as track faults and overheating engines.

Services are expected to be very busy, particularly to coastal destinations. This will make trains and buses feel hotter, even on air-conditioned vehicles.

TfW is recommending customers stay hydrated by taking a bottle of water while travelling. Free water refill points are available at Llandudno, Machynlleth and Cardiff Central stations.

Colin Lea, Transport for Wales’ Planning and Performance Director, said: “We continue to see very high demand for our rail services, particularly during periods of good weather. All available carriages are in service and where possible, we’re providing supplementary road transport.

“It’s now more important than ever to plan ahead using information our new website, our recently updated app or our social media channels.

“Passengers should consider whether they want to travel on trains that are likely to be full and standing, and use our Capacity Checker – an online tool that allows customers to see which trains are likely to have the most space available.”

Dan Booth, seasons delivery manager, at Network Rail Wales and Borders, said: “We do everything we can to limit disruption for passengers during hot weather, but safety is our number one priority.

“Speed restrictions are likely to be in place across many parts of Wales and Borders, as slower trains reduce the risk of damage to the tracks when they expand during extreme temperatures.

“We advise passengers to carry a bottle of water and please check journeys before travelling for any delays or disruption.”

Jo Foxall, Customer Engagement Director at Transport for Wales said: “Looking after our customers’ well-being so that they are still able to travel when they need to during the hot weather, is top of the transport industry's priorities over the next week.

“Taking a look at your journey options on the Traveline Cymru travel map to spend less time in the hot sun, keeping an eye on any disruptions and saving 0800 464 0000 in your phones if you need any travel advice while you're out and about could help make your journey run more smoothly.”