The alert includes Pembrokeshire, Carmarthenshire and Ceredigion.

The yellow warning takes effect from 5pm this evening, Saturday July 19 until 9pm.

The forecaster said: “Heavy rain and thunderstorms may cause some localised flooding and transport disruption.”

The Met Office is also advising:

  • There is a slight chance of power cuts and loss of other services to some homes and businesses

  • There is a small chance that homes and businesses could be flooded, causing damage to some buildings

  • Where flooding occurs, there is a slight chance of delays or cancellations to train and bus services

  • Spray and flooding could lead to difficult driving conditions and some road closures

  • There is a small chance that some communities will become cut off by flooded roads

  • There is a small chance of fast flowing or deep floodwater causing danger to life