A hosepipe ban has come into force in parts of southern England.
The move was imposed on Southern Water customers in Hampshire and the Isle of Wight from 17:00 BST.
This means that using hosepipes to water gardens, clean cars, fill ornamental ponds and swimming pools will not be allowed.
The restrictions are expected to last for three weeks. Similar measures are being introduced across Kent and Sussex after the driest July since 1935.
Anyone breaking the rules could face a fine of up to £1,000.
Southern Water said the decision to introduce the ban - which is the first in England this year - was a "vital step" to protect the habitats of the River Test and the River Itchen, where it extracts water.
Last month the company said river flows were about 25% lower than they should be for July.
Alison Hoyle, the company's director of risk and compliance, told the BBC she wanted to remind customers that there would be no restrictions on essential water use.
"We are hoping for substantial rain," she said. "At the moment we're saying we expect [the hosepipe ban] to be three weeks but we will need to monitor this closely depending on rainfall and river levels."
Portsmouth Water is not introducing a hosepipe ban but it urged its customers not to waste water.
The firm said it was keeping its position "under review" and monitoring the situation "on a daily basis".
How will you be affected by the hosepipe ban? You can share your thoughts by emailing [email protected].
Thames Water's customers have also been asked to use water "wisely".
The company said the next stage of its statutory drought plan would be to introduce a temporary use ban "which is likely to include hosepipes".
In a statement it added: "The timing will depend on the amount of water used by our customers, which determines the speed at which reservoir storage declines, and the amount of flow in the rivers, which determines how much water we can take to refill them."
Water is being transferred to Berkshire from north London to stop a hosepipe ban being introduced in the county, Thames Water previously said.
At an emergency meeting held last month, the National Drought Group moved England into "prolonged dry weather" status - the stage before a drought.
In Kent and Sussex about one million South East Water customers will face measures from 12 August.