The fan oven blowing over Manawatu will push temperatures towards 30 degrees Celsius this weekend, prompting warnings from local authorities.
MetService forecaster Matthew Ford said the hot, dry weather of the past week would continue in the region today and tomorrow.
There was potential for the mercury to touch 30C with hot northwesterly winds tomorrow.
Temperatures would be in the high-20s on both days, Mr Ford said.
Rain was forecast to set in on Monday but it was still likely to be warm.
Those hoping to beat the heat with a quick dip are being warned to be wary of high algae levels in Manawatu rivers.
Horizons Regional Council water quality scientist Logan Brown said the hot weather had kept the algae cover at Horseshoe Bend in Tokomaru at high levels. The signs remained up to advise people to avoid swimming at Horseshoe Bend and at the Mangatainoka River.
Testing on the Manawatu River near Maxwells Line showed it was currently safe but people needed to be vigilant, Mr Brown said.
"With the hot weather we are currently expecting, there is likely to be spots we don't monitor, where algae is blooming, so it is best for people to keep a lookout for musty-smelling, black, slimy mat-like growths on river beds.
"If you see these, it is safest for you and your dog to avoid using the river."
Mr Brown said the presence of algae did not mean the water was toxic.
"It is touching the black algae or ingesting it that is the issue," he said.
The consistent hot weather has also prompted MidCentral medical officer of health Dr Rob Weir to warn Manawatu residents to check regularly on those vulnerable to heat.
"The elderly, very young and those who are unwell - especially with heart disease or high blood pressure - are particularly vulnerable," he said.
He recommended people stay hydrated over the weekend and find places with shade and good ventilation.
A cool shower or bath was an effective way to cool off, and wet towels applied around the neck and arms could also be helpful to beat the heat, he said.
- Manawatu Standard
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