A yellow weather warning for thunderstorms is in place for Portsmouth for much of the day.
The Met Office has warned that thundery downpours could hit the city and the surrounding area between 2pm and 11.59pm today.
While the yellow weather warning is in place for Portsmouth, Gosport, Havant, Fareham, Waterlooville and Hayling Island, it cannot be predicted exactly where will be hit by the thunderstorms.
Currently the Met Office is forecasting cloudy weather with highs of 21C for Portsmouth today.
A Met Office spokesman said: ‘High temperatures may set off some heavy showers and thunderstorms, which in some places could be slow-moving and persistent, bringing a risk of flooding.
‘Should they develop, in the heaviest showers some places could see 30mm of rain in an hour, which would likely bring flooding impacts particularly should this fall on an urban area.
‘There would also be a smaller chance of impacts from lightning strikes.
‘As is the nature of showers, many places will miss them altogether, and it is not possible to say precisely where they will occur, but the warning area highlights the region at greatest risk.’
The Met Office issued the yellow weather warning earlier in the week.
Residents are being warned that if thunderstorms hit Portsmouth they could be torrential downpours and could lead to difficult driving conditions with the possibility of road closures.
The Met Office also warns that there is a small chance that homes and businesses could be flooded quickly, with damage to some buildings from floodwater.
And that there is a slight chance that power cuts could occur and other services to some homes and businesses could be lost.