It follows a ban from Yorkshire Water which began 11 July – the first of 2025 – with Thames Water planning a ban from 22 July.
Southern Water’s ban – affecting almost one million customers across Hampshire and on the Isle of Wight – will come into effect from 21 July.
In May, Southern Water, SES Water and Affinity Water told the BBC they did not expect to introduce water use restrictions, such as hosepipe bans, in 2025.
It comes as the UK has experienced three heatwaves so far this year, with the BBC Weather Centre confirming 1 July as the hottest day of the year when 35.8C was recorded in Faversham, Kent.
The Environment Agency has already said that some areas of the UK are either in drought or a “state of prolonged dry weather”, after the second driest spring on record for England and the sixth overall across the UK.
Periods of dry weather and low rivers can have consequences for the environment and wildlife,” the Environment Agency said.
Hot and dry weather can increase wildfires, severely damaging vulnerable areas of heathland and moorland,” a spokesperson said.
“Crop failure is also a major impact of drought while low water levels make navigation difficult on canals and some rivers.”
None of the water companies with hosepipe bans in place have specified exactly when restrictions will be lifted.