The muggy, showery weather is set to continue for the next couple of days after Rotorua experienced its hottest December day on record this week.
The National Institute of Water and Atmospheric Research said the temperature reached 28.4C on Monday to become the warmest December day on record forthe town.
Monday's temperature beat the old record of 28.3°C on December 28, 2015 with records going back to 1972.
MetService meteorologist Angus Hines said it was a static weather situation for Rotorua over the next couple days with warm and humid conditions expected.
"There is muggy air near the surface of the atmosphere with cooler air above it. This could produce thunderstorms around the region and potentially small bouts of hail."
Metservice warned of localised rain downpours of 25 to 40mm per hour "or possibly more".
In a statement this morning, the weather forecaster warned rainfall of this intensity could cause surface and flash flooding, and may lead to slips and hazardous driving conditions
Tomorrow will see a humid and cloudy start to the day with a risk of thunderstorms again in the afternoon.
