A water company has said its customers will not be permitted to use hosepipes and sprinklers when it implements the UK's first drought order for 11 years.
Sutton and East Surrey Water said the ban, which starts on Saturday, is for businesses as well as homes.
The ban will include watering sports grounds and washing cars, trains and aircraft with a hosepipe.
The company said restrictions were intended to reduce peaks in demand in order to safeguard supply.
But it said use of watering cans, buckets and commercial window cleaning using a hosepipe not connected to the mains, were exempt from the ban.
Mechanical vehicle washers would also be allowed providing they use recycled water, it said.
Michael Hegarty, operations director for Sutton and East Surrey Water, said: "If demand exceeded the amount of water available, customers would go out of supply."
He said the drought was serious because of two dry winters in the South East, leaving the natural underground storage at its lowest level.
"Normally spring rainfall does not reach the aquifer because it is absorbed by vegetation or lost by evaporation," he added.
"But May has been very wet so some water may get into the aquifer."
The company said restrictions would help preserve water resources in the event of a third dry winter.
Sutton and East Surrey Water serves 650,000 people in the South East.
On Thursday Southern Water, which covers large areas of south-east England, was granted a drought order for Kent and Sussex.
An order was also granted for the entire Mid Kent Water area.
Southern Water said the recent wet weather meant the company would not implement the order immediately, but neither company ruled out introducing restrictions later in the year.
Environment minister Ian Pearson, who granted the orders, said: "The rainfall we are seeing now and over the rest of the summer will have little impact on groundwater levels."