Hamilton and parts of Waipā district will be placed under alert level two water restrictions from tomorrow.
Sprinklers will only be permitted for use between 6am and 8am and between 6pm and 8pm, on alternate days.
That means houses with even street numbers are allowed use sprinklers on even days, with odd-numbered houses allowed to use sprinklers on odd days.
Hand-held hosing is permitted, but Hamilton City Council has warned if water consumption does not drop, further restrictions may be needed.
In a statement, the council's city waters manager, Maire Porter, said the city's residents had used almost 80 million litres on Monday.
"With the dry hot weather expected to continue we need to ensure we are using water sustainably, particularly when it comes to outdoor water use," she said in a statement.
"We know on some days up to half of the city's water usage is outside on lawns, gardens, pools and for washing vehicles and boats.
"If this level of demand continues, a move to water alert level 3 may be needed, which will mean no sprinklers are to be used at all."
In Waipā, the water services manager, Martin Mould, said the move would help to support small towns where water sources were at the mercy of the weather.
"Last summer's drought is still firmly in our minds as we make this move, we want to prolong our supply as long as possible," he said in a statement.
"Our residents are already making good strides in reducing their water use this summer, so we hope the small adjustment will be easy to do.
"Now is also a good time to address any leaks, turn off taps, and make other small changes to be mindful about how you use your water."
The restrictions affect Hamilton, Te Awamutu, Pirongia and Ōhaupō.
They also apply to some households in Waikato that receive their water supply from Hamilton.