Afternoon lake breezes were likely but they would not stop Rotorua from being one of the most settled areas in the North Island, he said.
According to the National Institute of Water and Atmospheric Research (Niwa), January temperatures in Rotorua peaked around the mid to late 20s in recent years, while mean temperatures were between 16C and 18C.
Niwa records showed 2013 was a particularly hot and dry January, with a maximum temperature of 27.5C, mean temperature of 17.4C and only 8.6mm of rain.
Last January, temperatures were down slightly but it rained far more, with a total of 52.2mm recorded over the month.
Niwa's latest outlook predicted Bay of Plenty temperatures to be near or above average and rainfall to be near average from January to March.
Nationally, there had been a far healthier mix of sun and rain so far this summer, compared to the previous four or five summers, Mr Duncan said.
"When the farmers are happy, the 'townies' usually aren't and when the townies are happy, the farmers usually aren't, but this summer has probably got the closest you get to having both sides happy.
"It's hard to explain to people that it's good to get one or two days of rain in the middle of your summer holidays but the thing is, it's good for the economy. A couple of days of rain will save you money at the supermarket."
The country would get "pockets of drought-like weather" but they would unlikely be consistent enough to be considered a drought, he said.
MetService meteorologist John Law said highs which had dominated New Zealand during the first week of January were expected to continue next week, bringing more warm and drier-than-usual conditions to most of the country.
"Following that, some welcome rain is signalled mid-month, with warmer northerlies producing a wet week over New Zealand," he said.
Warmer conditions would return by month end, bringing overall January temperatures to above average, he said.
Meanwhile, rainfall would be above normal for north-facing regions and normal to dry elsewhere, he said.
Year Hottest day Max. temp Mean temp Total rainfall
2000 22nd 24.6C 17.1C 78.6mm
2005 31st 28.1C 17.6C 23.4mm
2010 15th 25.6C 17.2C 172.2mm
2011 17th 27.7C 18.4C 423.8mm
2012 2nd 25.1C 17.1C 119.2mm
2013 7th 27.5C 17.4C 8.6mm
2014 31st 24.4C 16.3C 52.2mm
-Source: NIWA