Scattered heavy showers and thunderstorms are likely to develop on Saturday, initially over parts of North Wales and the southern part of North West 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.
The yellow warning for between noon and 7pm says travel and power could be disrupted in a few places.
It adds that some damage to a few buildings and structures from lightning strikes is possible.
There is a good chance driving conditions will be affected by spray, standing water and/or hail, leading to longer journey times by car and bus.
Some short-term loss of power and other services is likely
And there is a small chance of some flooding of a few homes and businesses.