Heavy rain across Lancashire could cause flooding, the Met Office has warned.
The national forecaster announced that downpours on Tuesday could cause "some disruption from flooding" and told the public to prepare.
A Yellow Weather Warning is now in place across much of North West England and Wales between 4am and 11pm tomorrow.
Storm clouds are expected to move northeastwards across the region during Tuesday, with some areas seeing up to 70mm of rain in less than six hours.
Strong winds and thunder and lightning are also predicted.
Today the Met Office warned residents in affected areas that some buildings may be damaged by floodwater, and that isolated communities may be cut off by flooded roads.
They said delays and cancellations to rail and bus routes was possible, and that driving conditions could be made difficult because of spray and surface water.