Aotearoa's swimming spots are expected to stay clean and clean over the coming holiday period.
Water monitoring organisation Land Air Water Aotearoa (LAWA) says warm and dry weather will help keep many of the country's beaches and rivers safe.
While Christmas Day will be mostly fine across northern and central New Zealand, southerly winds are expected to bring unsettled conditions farther south, according to MetService forecasts.
LAWA science lead Anna Madarasz-Smith said water quality could be impacted after heavy rain as pollution washed out through waterways and into the sea.
"Water quality changes, so a big part of keeping you and your family safe is knowing what to think about before you decide where to swim," Madarasz-Smith said.
People should avoid swimming for at least two days following downpours in order to be sure water quality is safe, she said.
Hotter weather could also increase the chance of potentially toxic algae blooms in freshwater.
Swimmers should check LAWA's 'Can I swim here?' online tool prior to entering the water.
It uses a traffic light system of red, yellow and green to show the health risk of swimming at a chosen site based on most recent monitoring result.
"LAWA has over 750 swimming sites so there is always going to be somewhere to swim near you, so avoid swimming in areas where the icon is amber or red from weekly results," Madarasz-Smith said.