A weather alert warning of heavy rain and possible flooding has been issued for Greater Manchester.
The 'yellow' warning will be in place tomorrow (Tuesday) from 12am to 12pm. The worst of the weather expected to hit during morning rush hour.
According to the Met Office, there could be damage to buildings and potential disruption to public transport.
The warning area covers Greater Manchester, Warrington, Merseyside, Cheshire and Lancashire.
A statement read: "Areas of heavy rain may affect some areas. Around 15 to 20 mm of rain may fall in an hour, with 30 to 40 mm in three to four hours possible in a few places."
A 'yellow' weather alert, warning of thunderstorms, is already in place for today (Monday), from 12am until 12pm.
Unsettled conditions are expected across much of the country.
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There could be isolated heavy thunderstorms from midday. The worst of the weather is expected to clear in northern areas by the afternoon.
Forecasters are warning there could be flooding to homes and businesses, disruption to train and bus services as well as a slight risk of power cuts.
A statement on the Met Office website said: "An area of heavy thundery rain is expected to move northwards across England and Wales during Monday, probably clearing northern England through the course of the afternoon.
"Isolated heavy thunderstorms may then develop across parts of England and Wales during the afternoon. Further heavy thundery rain may then arrive into parts of southern and southeastern England and East Anglia during the evening.
"In areas affected by the thundery rain, 15 to 30mm may fall widely and 30 to 40mm of rain may fall over parts of northern England. In areas affected by isolated heavy thunderstorms, 30 to 40mm of rain may fall in an hour in a few places."
The Met Office says Monday will be 'very humid', with temperatures reaching 23C and dipping to 15C overnight.
Tomorrow (Tuesday) will feel warm, with bright, sunny spells and highs of 21C.
The rest of the week should be dry and sunny, with temperatures 'continuing to rise'.
Bonnie Diamond, a meteorologist for the Met Office, said: "Heavy thunder storms may develop across the UK and Wales this afternoon. 30-40mm of rain may fall in a few places.
"Some areas might avoid these thundery showers, but if you do get them that could lead to a lot of rain in a short space of time and flooding in some places.
"Tomorrow we are expecting a broad area of heavy rain from about 4am to 5am in Manchester. There is a warning in place for the heavy rain from 12am tomorrow until midday. Early commuters will see heavy rain and later in the morning it will turn to patchy rain.
"That gradually clear tomorrow afternoon. It will still be a cloudy evening but with some warmer weather arriving for Wednesday."
It will start to become very warm and it will remain on the humid side, with highs of 24C by the end of the week.
