The Met Office has extended two days of thunderstorm weather warnings into a third day.
Forecasters originally said thunderstorms could hit Wirral on Monday and Tuesday.
But experts have said thunderstorms could also hit the area through Wednesday too.
Thunderstorms are expected to hit the country bringing heavy rain and frequent lightning.
Heavy rain could lead to some flooding of houses as up to 80 mm of rain could fall in just three hours.
Damage to buildings and power cuts could occur where there are lightning strikes and hail.
A forecaster at the Met Office said: “Areas of thunderstorms are likely to develop over parts of the UK or nearby continent during the middle of next week, and will generally track north or north-westwards, potentially affecting all parts of the UK at some points during this period.
“Whilst the most intense thunderstorms, in some instances associated with large hail, will most probably be those triggered by the high temperatures of the day over England and Wales, other areas of storms producing heavy rainfall and frequent lightning could reach further north across Scotland and Northern Ireland.
“These could occur at any time of the day. Where the storms occur, rainfall totals of 30-40 mm could fall in an hour, with some locations potentially receiving 60-80 mm in 3 hours, although these will be fairly isolated.”