Most of the UK is also included in the warning, with the entire country on warning to prepare for storms.
The Met Office forecast for Merseyside states: “There is a risk of severe thunderstorms during this period which could be interspersed with brighter and sunny periods.
“Stay warm and humid day and night. ”
The warning, covering Monday through Wednesday next week, says: “Some places are likely to see severe thunderstorms early next week – but there is significant uncertainty as to the location and when.
“There is a small chance that homes and businesses will be flooded quickly, with some buildings being damaged by flood water, lightning strikes and large hail.
“When floods or lightning strikes occur, there is a risk of delays and cancellations on public transport.
“Spray and flash flooding could lead to difficult driving conditions and an increased risk of accidents.
“There is a low risk that power outages will occur and that other services to some homes and businesses will be lost.
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“There is a small chance that rapid or deep floodwaters could be life threatening. ”
Temperatures in Liverpool are expected to climb into their 20s over the weekend as the heatwave sets in.
Dry and sunny weather is expected to dominate this weekend, but the warm weather is expected to end with a series of thunderstorms, according to the Met Office.