Police urged motorists to drive to the conditions, especially if rain hit dry roads.
Campgrounds have reported being full for much of the holiday period, although motel bookings were slightly down on last year, possibly due to the rising popularity of Airbnb.
Tony Bullot, Accommodation NZ's Bay of Plenty accommodation sector group chairman, said Tauranga motel bookings were "looking good" right through to end of January.
"But overall we have seen a decrease in demand compared to the same time last year. It's less than 10 per cent but it still a noticeable drop and some of the decrease we suspect is due to the rise in the use of Airbnb," he said.
At the Mount Maunganui Beachside Holiday Park, Aucklanders Jan Davison, and her sister and brother-in-law Denise and Andy Blanchard, are spending three weeks at their regular tent site.
"We have been coming here for about 40 years and look forward to every year. We just love it," Davison said.
"It's our happy place. The place we can chill out, forget about all the cares of the year and all things to do at home, and recharge our batteries for the year ahead," she said.
Denise Blanchard said her daughter and mother, who had also holidayed there with her late father for six decades, would also be joining them during their three-week stay.
"It's like a second home to us. Why would you want to go anywhere else? It's such a beautiful place and we love catching up with the same people each year."
A spokeswoman from Mount Maunganui Beachside Holiday Park said the park was full until the end of January, with all 200 powered sites occupied by 481 people.
Guest numbers were set to grow to about 550 over the next few days, she said.
Papamoa Beach Top 10 Holiday Resort general manager Rebecca Crosby said there were 600 people holidaying at the resort.
"We will be pretty full from December 29 to the second week of January, with just a few spots here and there but nothing much available," she said.
Crosby said between 1000 to 1100 guests were expected to stay during that period.
"I always tell my staff we're in the business of creating memories. That's why people want to come back to the same site or unit year after year, and some people return four or five times in the year," Crosby said.
Rachel Butterworth, one of the owners of Katikati's Sapphire Springs Holiday Park, said bookings this year for the 60 powered sites were up on last year.
"Currently we still have a few campsites free. We also have a large field in front of the park which has unpowered sites and where we can accommodate a few more campers."
Butterworth said she expected to be full from New Year's Eve but weather played a key role.
A Waihi Beach Top 10 Holiday Resort employee said the resort was fully booked until mid-January.
About 700 people were occupying the 60 powered sites, 32 units and 60 permanent caravans, with holidaymakers coming and going from the latter, she said.
"It's a great to see this amount of bookings at the start of what we hope will be a busy summer season," she said.
Peak heavy traffic on Bay highway hotspots:
State Highway 2 between Tauranga and Katikati
- Today: Westbound from 11am to 2.30pm. Eastbound between 10am and 12pm.
- December 28: Westbound from 11am to 3.30pm. Eastbound between 10am and 1.30pm.
- December 29: Westbound from 11am to 4.30pm. Eastbound between 10.30am and 2.30pm.
- December 30: Westbound from 10.30am to 5pm. Eastbound between 10am and 5pm.
- New Year's Eve: Westbound from 11am to 12.30pm.
- New Year's Day: Westbound from 11am to 3.30pm. Eastbound between 1.30pm and 4.30pm.
State Highway 29 Kaimai Range
- Today: Eastbound from 11am to 12.30pm.
- December 30: Eastbound from 2pm to 4pm.
- January 2: Westbound between 5pm and 6pm
- January 3: Westbound between 10.30am and 2pm.
State Highway 2 between Paeroa and Waihi
- December 28: Eastbound between 11am and 1.30pm
- New Year's Eve: Eastbound between 12.30pm and 3.30pm.
- January 2: Eastbound between 11am and 4.30pm. Westbound from 10.30am to 4pm.
- January 3: Westbound from 11am to 4pm.
