Wirral has been placed on a yellow weather warning for Thunderstorms.
Thunder, lightning and heavy rain is expected from 12pm to 7pm today.
Forecasters warn that 20mm of rain could fall in less than an hour as thunderstorms move over the area.
The severe weather could mean that there will be bad driving conditions from heavy rain as well as flooding.
Lightning strikes to buildings could be possible with some power outages.
The Met Office say: “Scattered heavy showers and thunderstorms are likely to develop on Saturday, initially over parts of north Wales and the southern part of northwest England around midday, and then later in the afternoon across Cumbria and the north Pennines.
“Most of these will not last long but could produce 20 mm rain in less than an hour, leading to some localised flooding.
“Lightning strikes and hail will be additional hazards in places. The showers and thunderstorms will slowly die out from the south later this afternoon and through the early evening.”