Weathermen have issued an alert that thundery showers will hit southern England this afternoon.
The Met Office included the Portsmouth area in its severe weather warning as forecasters said a very warm day could be marked by heavy downpours.
A spokesman said: ‘A very warm, locally hot, day is expected, although cloud will gradually build, bringing scattered showers later, perhaps turning heavy and thundery in places.
The Met Office predicated the weather would turn at around 1pm on a day on which maximum temperatures are expected to rise as high as 28C.
The forecast is: ‘Tonight: Showers, thundery in places, will continue overnight, with possible downpours. Showers will turn increasingly isolated, before gradually easing away later. Elsewhere, some clear spells are likely. Feeling rather muggy. Minimum Temperature 14 °C.
‘Tomorrow: Sunny spells, with isolated showers likely to develop later. These could again be heavy at times, perhaps with thunder. It will remain warm, but perhaps less so than on Tuesday. Maximum temperature 25C.