Mr Williamson had been rebooked on a flight at 6.45am today from Rotorua to Wellington.
"It will be an early start," he said.
By yesterday afternoon, Andrew Ravenscroft faced three flights to make it back to his hometown of Dunedin.
"I'm a long way from home," he said. "I was due to fly out at 5.05pm and got in the queue at about 4.30pm, and that's when we found out there were problems. When we left the factory just after 4pm the website was still saying everything was fine."
However, Mr Ravenscroft said he was not too frustrated.
"It's just one of those things really, we can't control the weather."
Heavy rain, hail, thunder and lightning were reported in the Kaimai Ranges and at Pyes Pa.
Flooding occurred at Tautau Stream Bridge, on Pyes Pa Rd. Fiona Morrison and her two children have lived opposite the bridge for 11 years.
"The weather was atrocious today," she said. "It started out really misty and foggy this morning but the really heavy downpours started around 1pm. That's when the flooding started and it's been on and off all day."
Miss Morrison, whose driveway had flooded, said the area was an accident blackspot, especially in the wet. She added her home had been without power all day.
Although the weather was bad, she had seen worse. Five years ago the road gave way after a severe storm, she said.
"It just disintegrated. We had pieces of road in our garden all around our house."
Bay of Plenty Civil Defence upgraded its threat status to yellow in light of severe thunderstorm warnings issued by the MetService.
At 2.07pm, the MetService weather radar detected severe thunderstorms near Matamata, Waharoa, the Kaimais, Te Poi and Hinuera.
These storms were moving towards the southeast and were expected to lie near Rotorua, Mamakau, the Waikite Valley, Rotoiti and Lake Tarawera.
The thunderstorms were expected to be accompanied by very heavy rain, damaging wind gusts and possible tornadoes.
Western Bay of Plenty road policing manager Senior Sergeant Ian Campion said his officers had come across heavy downpours in the Kaimais and on State Highways 33, 36 and 2 while patrolling the region.
"It's been pretty much right across the Bay," he said.
"There was some surface flooding on State Highway 29 close to Kaimai School and further up the Kaimais towards the summit. There's also been the odd downpour of hail."
Meanwhile, a spokesperson for the fire service said a small tornado went through Sunnex Rd at Hamurana, in Rotorua, at 3.20pm yesterday.
Forty children, understood to be from Mokoia Intermediate, and 13 adults were at a horse riding class and were evacuated to a nearby property. Some of the properties on Sunnex Rd were also evacuated.
MetService forecaster Dan Corbett said today would bring a cooler, fresher feel, with a few showers and a breezy southwest wind.
"By Saturday, bar one or two early showers, you'll be able to bring out the sunglasses again."
Sunday would be fine and dry, he said.