The Environment Agency has issued a flood alert for Calderdale as the region prepares for thunderstorms to hit.
A flood alert is now in force for the River Calder Upper catchment area with flooding possible from Todmorden to Brighouse.
A spokesperson said: "This flood alert has been issued in response to the forecast for heavy showers and thunderstorms that could affect areas throughout South and West Yorkshire from around 5pm this evening (Thursday 26 July).
"It is not possible to predict the precise location of these thunderstorms, but where they occur there’s a risk of localised surface water flooding and flooding from smaller rivers affecting roads, homes and businesses.
"This means that we are taking the precautionary measure of issuing flood alerts for faster responding rivers and surrounding communities.
"Our staff are monitoring the situation and our field teams are working with partners to ensure that defences are clear of obstructions.
"Given the speed at which levels in the faster responding rivers may rise, we may not have time to issue all flood warnings before the onset of any flooding.
"Please stay aware of your surroundings and do not put yourself at risk. Be prepared to act on your flood plan."