A hosepipe and sprinkler ban is being imposed on the Isle of Wight for the first time in 30 years.
Southern Water said the restrictions, which affect more than 65,000 homes, will come into force on 24 March.
"These precautionary measures are being brought in to ensure that we can continue to supply all our customers with drinking water," said a spokesman.
The decision comes only days after Thames Water imposed a similar ban on its customers.
Southern Water said the restrictions follow two "exceptionally dry winters" in the south of England.
A spokesman said: "Rainfall in February and March has helped the situation but even above average rainfall until summer will not ensure that Southern Water can meet demand without the restrictions."