The Met Office has issued a yellow thunderstorm warning covering nearly every part of South Wales, including Cardiff, Swansea, Newport, Rhondda Cynon Taf, Bridgend, Carmarthenshire, and Powys.
The warning will be in effect from midnight until 10am on Friday, June 26.
The warning states there is a “small chance” of homes and businesses flooding, with damage from floodwater, lightning strikes, hail or strong winds.
Sudden flooding and spray could make driving “difficult,” and there is a slight risk of train and bus delays or cancellations.
Thunderstorms are expected to move northeastwards across parts of England and Wales during the early hours of Friday, clearing during Friday morning.
While some areas are expected to escape the worst, the storms could bring gusty winds up to 60mph, frequent lightning, hail, and heavy rain.
The Met Office has warned that rainfall could reach 15-20mm in just one hour.
The UK public body explained that the warning has been classed as “very low likelihood and medium impact.”
To help residents stay safe, advice has been issued by the Met Office.
A spokesman for the Met Office said: “Consider if your location is at risk of flash flooding. If so, consider preparing a flood plan and an emergency flood kit.
“Prepare to protect your property and people from injury. Before gusty winds arrive, check to ensure moveable objects or temporary structures are well secured. Items include; bins, garden furniture, trampolines, tents, gazebos, sheds, and fences.
“Give yourself the best chance of avoiding delays by checking road conditions if driving, or bus and train timetables, amending your travel plans if necessary.”
It is also recommended that people prepare for potential power cuts by gathering torches, batteries, a mobile phone power pack, and other essential items in advance.
If you find yourself outdoors during a thunderstorm and hear thunder, the Met Office advises seeking shelter inside a safe, enclosed structure such as a car.
It warns against sheltering under or near trees or tall objects, as these are more likely to be struck by lightning.
Those on elevated ground should move to lower areas as soon as possible.
The Met Office also urges the public to keep up-to-date with weather changes, as alerts and conditions can shift rapidly.
Beyond the immediate warning for Friday, an amber warning is in place for Saturday.
However, earlier in the week, red warnings were issued for Thursday and Friday, followed by an amber warning for Saturday.
This suggests that conditions have improved since the most severe alerts earlier in the week.
As the thunderstorm warning is in place for much of the country, similar advice has been shared for other affected regions.
In the South West of England, residents have also been told to prepare for power outages and flash flooding.
Suggestions include having an emergency flood kit ready and ensuring outdoor items are secured.
In the North East, the Met Office reminds people that weather warnings can change at short notice and urges everyone to check the latest forecast for their area.
With the potential for disruption, the Met Office continues to emphasise the importance of staying informed and prepared.
Residents in South Wales and other affected areas are advised to monitor updates and take precautions as needed to reduce the risk to property and personal safety.
