Waihi Beach volunteer fire chief Ian Smith said his brigade were called to people in a car, trapped in floodwaters at Emerton Rd.
Mr Smith said he anticipated to be on the job through the night as the "torrential rain" showed no sign of letting up.
"We have a lot of flooding. We have Three Mile Creek right at the point of breaching its banks, half of Beachaven is under water, a lot of houses are having constant flooding - surface flooding but flooding through the roof as well.
"We have had so much hail. In fact I'm standing in hail at the moment which is probably 25cm thick, if not thicker. That's just standing on the side of the road."
Mr Smith said he couldn't remember the last time he'd seen weather like that hit Waihi Beach. "It's an absolute weather bomb. People have water coming out through their light fittings."
Between 6.30pm and 7pm Waihi Beach firefighters were called five times, resulting in at least three pensioners being evacuated from flooded homes and taken in by family.
"I saw one car with water up to its window," Mr Smith said.
Volunteer firefighters from Athenree came to the aid of their colleges.
The Athenree brigade also received several calls for assistance as the weather hit.
Waihi Beach Beachaven Holiday Park manager Yvette Johnson said the rising river was a big concern.
"It's knee deep. We've got a couple of motel units flooded. The state of the vans, we don't know the extent of damage until it's light but we are aware of a couple that are damaged."
Ms Johnson said there was little they could do.
"We have a pump but that can't keep up with the water, it's just not stopping."
Ms Johnson said the rate of water was worse than the New Year flooding they experienced.
Four elderly people were evacuated from their units at the park because they became filled with mud and sludge, Ms Johnson said.
They were being looked after at the park's other motel units.
Sergeant Dan Roser of Tauranga police said they had been called to a few street flooding incidents at Mount Maunganui.