A yellow weather warning issued for south Wales on Thursday (August 1) due to thunderstorms has now been extended.

The Met Office has issued a yellow weather warning due to heavy showers and thunderstorms which will now be in place across most of south Wales for nearly 24 hours from 1am to 11.59pm on Thursday (initially only starting at 12pm).

The heavy showers and thunderstorms are likely to cause flooding, travel disruptions, loss of power and pose a danger to life, according to the Met Office.

The weather warning will affect most of South Wales including Newport, Blaenau Gwent, Monmouthshire, Caerphilly, Cardiff and Vale of Glamorgan. 

These thunderstorms will follow some warmer weather, with temperatures set to reach highs of 28 degrees in some areas of south Wales on Monday, Tuesday and Wednesday (July 29, 30 and 31).

What to expect from the yellow weather warning in South Wales

The Met Office said the yellow weather warning was issued across South Wales due to "multiple rounds" of heavy showers and thunderstorms forecast for Thursday which may cause some disruptions.

The thunderstorms associated with the yellow weather warning are also set to cause:

  • Difficult driving conditions and some road closures due to spray and sudden flooding
  • Chance of cancellations and delays to train and bus services as a result of flooding or lightning strikes
  • Power cuts and disruptions to other services in homes and businesses
  • Homes and businesses could be flooded quickly, with damage to some buildings from floodwater, lightning strikes, hail or strong winds
  • Fast flowing or deep floodwater could cause danger to life

A Met Office spokesperson added: "Whilst there is some uncertainty, thunderstorms may affect southeast England during the early hours of Thursday, perhaps also extending into parts of East Anglia.

"Where these occur, rain accumulations of 25-40 mm are possible in 1 hour, with a small risk of over 60mm in 2-3 hours, and accompanied by frequent lightning at times.

"Elsewhere, an area of showery rain is likely to develop and move northeastwards across parts of Wales, the Midlands and northern England.

"This will be heavy and perhaps thundery at times, persisting through Thursday morning before easing towards midday.

"Some areas could receive rain accumulations of 25-50 mm over the course of a few hours.

What different Met Office weather warnings mean

"Scattered heavy showers and thunderstorms are then expected to develop through Thursday afternoon and evening across parts of central, southern and eastern England, and perhaps also south Wales.

"These have the potential to produce 50 mm or more in 1-2 hours, along with gusty winds, large hail, and the risk of surface water flooding."

Everywhere in Wales set to be affected by yellow weather warning

Areas of Wales set to be impacted by the yellow weather warning issued by the Met Office are:

  • Blaenau Gwent
  • Bridgend
  • Caerphilly
  • Cardiff
  • Carmarthenshire
  • Ceredigion
  • Conwy
  • Denbighshire
  • Flintshire
  • Gwynedd
  • Merthyr Tydfil
  • Monmouthshire
  • Neath Port Talbot
  • Newport
  • Powys
  • Rhondda Cynon Taf
  • Swansea
  • Torfaen
  • Vale of Glamorgan
  • Wrexham

See exactly where in south Wales the yellow weather warning for heavy showers and thunderstorms will be in place.See exactly where in south Wales the yellow weather warning for heavy showers and thunderstorms will be in place. (Image: Met Office)

How to prepare for the yellow weather warning and thunderstorms in South Wales

The Met Office has issued advice on how to prepare for the yellow weather warning and the risks it poses.

A Met Office spokesperson 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.

"People cope better with power cuts when they have prepared for them in advance. It’s easy to do; consider gathering torches and batteries, a mobile phone power pack and other essential items.

"If you find yourself outside and hear thunder, protect yourself by finding a safe enclosed shelter (such as a car).

RECOMMENDED READING:

"Do not shelter under or near trees, or other structures which may be struck by lightning. If you are on an elevated area move to lower ground.

"Be prepared for weather warnings to change quickly: when a weather warning is issued, the Met Office recommends staying up to date with the weather forecast in your area."

The yellow weather warning will be in place across South Wales from 1am to 11.59pm on Thursday, August 1.