A weather warning has been issued for rain across the North West on Tuesday afternoon.
As the region prepares for a heat wave, forecasters have issued a yellow warning for rain, including Lancashire and Blackpool.
Met Office experts say outbreaks of showery rain could turn torrential and thundery across parts of the north of England.
They say that, while most places will miss the worst, there is also a risk of large hail, frequent lightning and strong winds.
It could lead to flash flooding and disruption to travel.
The warning is in place from 2pm until 11pm on Tuesday.
A statement from the chief forecaster said: “A very warm and humid air mass is in place across much of the UK, with conditions marginal for thunderstorm development this afternoon as temperatures rise.
“Northern England and southeast Scotland are currently judged the most likely area to see scattered thundery downpours but even here many places will have no more than light rain.
“However, where storms do form, there is a lot of moisture and energy available, with the risk of more than 30mm of rain in around an hour, large hail and frequent lightning.”