Napier residents have been urged to conserve water, with the city's reservoirs at "critically low" levels.
Napier residents were warned their water could run out by tonight, after a warm weekend saw the city's reservoirs drop critically low. A total watering ban was also put in place for the rest of the week.
Residents have taken to social media questioning how levels dropped so rapidly.
Council director infrastructure Jon Kingsford said staff had been monitoring levels across the weekend, and Friday and Saturday levels had been ok.
"But on Sunday we took a big hit with our water use pattern. One issue of concern is the high number of people leaving hoses on at night, which is having a hugely negative impact on water levels."
On whether there were checks in place Mr Kingsford said council were "constantly monitoring the situation", but when asked how water levels then become critical before residents were urged to start conserving water, he said council had acted quickly upon discovering the low levels.
"The normal pattern is that the reservoirs recover overnight. Last night that didn't happen. They were checked this morning, levels were critical, and we acted straight away."
Residents were warned on Monday afternoon if they did not act to conserve water, "we run the very real risk of running out of water at some stage soon. Maybe even tonight".
Mr Kingsford said this was "an outside possibility if we don't get the response we need as we are using water faster than we can pump it into our reservoir from the aquifer".
"We are following the response plan, which is to advise our community and try and lower city usage as quickly as possible," he said.
Napier's water is drawn from the Heretaunga aquifer, and dispersed through a reticulated water supply. There are 10 wells drawing the water, 8 reservoirs and 18 pump stations.
This move is a contrast to the past summer, when Napier was one of the few areas around Hawke's Bay where water use was not restricted.
Although considered, restrictions were staved off until an E.Coli scare at the Enfield Rd reservoir in February.
Level two restrictions were put in place after the positive reading shut down the reservoir and saw water levels drop to critically low levels as the council's other water assets were placed under pressure.
Although summer started with a bang over the weekend this is just a hint of what's to come -with Hawke's Bay summers often breaking 30C.
Sunday was the hotter day, Metservice meteorologist Hannah Moes said, with Hastings one of the warmest spots in the country, reaching 28C in the early afternoon, while Napier was at 26C. Napier's high on Saturday was 24C.
These balmy temperatures are set to continue this week - tomorrow is set to reach 28C again in Hastings, and a high of 27 in Napier.
Ahead of the real summer, Napier City and Hastings District councils launched a joint conservation campaign, aimed at delaying or avoiding region-wide water restrictions.
Water consumption lifts by up to 70 per cent in summer months, and the supply is already struggling to cope.
Council staff were briefed on lowering water usage around parks and reserves. Non-potable water is used in some areas to irrigate city grounds and gardens, so the town supply was not affected.
The campaign will run from December until March.
This warning comes days after the city's water supply was dosed with chlorination for an indefinte period.
On Friday chlorine was added to the Otatara reservoir - which servies around 200 housholds - following a positive E.coli reading. Chlorine has been added to the city's water supply twice this year after positive E.coli readings at two other reservoirs.
Napier is not the only area being hit with low water levels - the balmy weekend meant water users in New Plymouth and Wellington were faced with restrictions.