The Met Office has issued yellow weather warnings for rain over the next two days, which may cause travel disruptions and flooding.
The first warning covers areas from Plymouth to Manchester, including parts of north-west and south-west England, Wales, and the West Midlands.
This alert is active from 6 pm Tuesday until midday Wednesday. During this period, most areas will receive 10 to 20mm of rain, but some could see as much as 50 to 80mm in just six hours.
Heavy rain is expected to develop in southwest England during late Tuesday afternoon, intensifying as it spreads northward through the evening and overnight into Wednesday.
Isolated thunderstorms, with a risk of lightning, are also possible in southern parts of the warning area, adding further hazards.
Residents are advised to prepare flood kits as the Met Office warns of potential power cuts.The second warning affects Northern Ireland, starting from midnight until 6 am on Wednesday, particularly targeting County Armagh and County Down.
Rain is set to move across Northern Ireland from Tuesday evening and will clear by Wednesday morning.
South-eastern areas of Northern Ireland are expected to see 20 to 30mm of rainfall, but some higher ground, especially in South Armagh, South Down, and the Mourne Mountains, could receive between 50 and 80mm.
The Met Office has advised residents to prepare for potential flooding and travel delays.
There is a slight chance of power outages and isolated communities being cut off due to flooded roads.
People are encouraged to check if their properties are at risk of flooding and consider preparing a flood plan and emergency kit as precautionary measures.