The Met Office has issued an amber warning for Carmarthenshire for this evening.
Amber is the second most severe warning the Met Office has, below red.
It is expected that severe thunderstorms will likely produce torrential downpours, flooding in some places and frequent lightning.
The warning is in place between 4pm on Thursday, May 31 and 6am on Friday, June 1.
A spokesperson said: "Flooding of homes and businesses is likely and could happen quickly, with damage to some buildings from floodwater, lightning strikes, hail or strong winds."
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