An Amber weather warning for extreme heat has been issued by the Met Office for Wales.
A hot spell is likely to develop from Sunday, likely peaking early next week, leading to widespread impacts on people and infrastructure.
The warning is in place from between between 00:00 (UTC+1) on Monday, 18 July and 23:59 (UTC+1) on Tuesday 19 July.
Meanwhile the Met Office has issued its first red extreme heat weather warning across England, ahead of scorching temperatures on Monday and Tuesday.
The national forecaster warns of “exceptional hot spell on Monday and Tuesday leading to widespread impacts on people and infrastructure.”
The red warning, which is in place on Monday and Tuesday, covers London and the Midlands and goes as far north as Manchester and York.
BBC Weather presenter Matt Taylor said there was an "increasing likelihood" the UK record high would be broken.
The highest recorded temperature in the UK was 38.7C in Cambridge in 2019.
Mr Taylor said while it was not guaranteed, it was the first time there had been a realistic possibility of hitting 40C in the UK.
People are being urged to stay hydrated, look out for vulnerable people, keep curtains closed and stay out of the sun in the middle of the day.
The heat is expected to increase pressure on the NHS, with the government's Cobra emergency committee holding a meeting on Thursday about how to prepare for it.
The Met Office said the hot weather was caused by high pressure over the UK and hot air flowing from southern Europe.
The areas of Wales affected by the Amber warning:
- Carmarthenshire
- Ceredigion
- Conwy
- Denbighshire
- Flintshire
- Gwynedd
- Isle of Anglesey
- Neath Port Talbot
- Pembrokeshire
- Powys
- Swansea
- Wrexham
What to expect
- Adverse health effects are likely to be experienced by those vulnerable to extreme heat. Government advice is that 999 services should be used in emergencies only; seek advice from 111 if you need non-emergency health advice.
- The wider population are likely to experience some adverse health effects including sunburn or heat exhaustion (dehydration, nausea, fatigue) and other heat related illnesses
- Some changes in working practices and daily routines likely to be required
- An increased chance that some heat-sensitive systems and equipment may fail, potentially leading to localised power cuts and the loss of other services to some homes and businesses
- More people are likely to visit coastal areas, lakes and rivers leading to an increased risk of water safety incidents
- Some delays to road, rail and air travel are possible, with potential for welfare issues for those who experience prolonged delays.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here