The Met Office has issued an amber extreme heat warning for parts of south-east Wales as forecasters warn temperatures could climb into the mid-30s next week.
The warning comes into force at 1am on Monday, 22 June and remains in place until 11.59pm on Tuesday, 23 June, covering Cardiff, Newport, the Vale of Glamorgan, Bridgend, Caerphilly, Rhondda Cynon Taf, Merthyr Tydfil, Blaenau Gwent, Torfaen and Monmouthshire.
Meteorologists say the hot spell will peak on Monday and Tuesday, bringing potentially significant impacts to public health, transport and infrastructure.
According to the Met Office, temperatures are expected to reach the mid-30s Celsius in some locations, while overnight temperatures may remain above 20°C in urban areas, offering little relief from the heat.
Forecasters have warned that vulnerable people are likely to experience adverse health effects, while the wider population could also be affected by heat-related illnesses including sunburn, dehydration, heat exhaustion, nausea and fatigue.
The Met Office said: “Following very warm weather on Sunday, very high temperatures are expected on Monday and Tuesday and will likely bring widespread impacts to people and infrastructure.
“In addition to high daytime maxima, temperatures overnight will remain very warm, especially in larger urban areas, and it will also feel humid.”
The warning highlights a number of potential impacts, including increased pressure on transport networks, with delays possible on roads, railways and at airports. There is also an increased risk of power outages and disruption to services if heat-sensitive equipment fails.
Authorities are also warning of a greater risk of water-related incidents as more people head to beaches, rivers and lakes to cool down during the hot weather.
The Met Office says some people may need to alter their daily routines and working practices to cope with the extreme conditions.
While the most intense heat is expected on Monday and Tuesday, forecasters say some areas could continue to experience very high temperatures into the middle of next week, although there remains some uncertainty over how widespread the heat will be.
Residents are being urged to stay hydrated, avoid prolonged exposure to the sun during the hottest part of the day, and check in on elderly relatives, neighbours and others who may be particularly vulnerable to the effects of extreme heat.
