The road through the Karangahake Gorge between Waihi and Paeroa has reopened after being closed since yesterday by rising river levels.

Most other roads hit by flooding and slips in parts of Waikato and Bay of Plenty have also reopened, but the NZ Transport Agency is urging motorists to take care on the roads.

Clean up work following the recent severe weather was under way, and motorists were advised to take care until the work was finished, NZTA said.

On State Highway 2 through the Karangahake Gorge "extreme caution" was needed as the surface was "very slippery" and there were small slips.

While both lanes had reopened along SH2 in Papamoa between Bruch Rd and Domain Rd, the northbound land would be shut between 7pm and 6am for overnight repair works.

A 50kmh temporary speed limit would remain in place until the road surface had been repaired, expected to take until the end of the week.

Late this afternoon NZTA acting state highway manager Karen Boyt said the agency would continue to monitor all roads in the area as rain eased off today and tomorrow.

"If drivers must travel we urge that they take extreme care on the highways, drive to the conditions, and allow more time for their journeys so that they can reach their destination safely."

Waikato Regional Council said its main flood management focus for the next few days would be on the Piako, Waihou and Waitoa Rivers, and the lower Waikato River, which remained heavily swollen following recent rains.

Rain has eased off in those catchments and the weather forecast for the next few days was looking better.

At the same time, heavy volumes of water would continue to flow down those rivers as catchments drained.

Heavy flows were expected to be particularly significant in the Piako and Waitoa Rivers in coming days, with levels likely to approach those seen during floods in 2008, the council said.

Shut floodgates due to high river levels could limit drainage, meaning surface water could build up on paddocks in many areas.

"The water will take some time to work its way through the system and there is always potential for more rain to fall on the saturated catchments," emergency management officer Greg Ryan said.

A heavy rain warning remained in place for Gisborne, with MetService predicting 30mm to 40mm could fall in the nine hours to 6pm. Most of that was expected north of Tokomaru Bay and inland and south of Gisborne City.

A low pressure system lying east of the North Island was directing moist easterlies and rain onto the region, the MetService said.

Yesterday motorists were trapped, farms flooded, and roads and schools closed as the rain-laden front swamped Waikato, pushing the region's waterways to bursting point.

Emergency services were yesterday flat out dealing with fallen trees, traffic control and crashes in the slippery road conditions.

Up to 260mm of rain fell on the Coromandel between midnight Sunday and 3pm yesterday.

Northern fire communications spokesman Jaron Phillips said the Fire Service was busy all day yesterday dealing with crashes and flood-related callouts.

In Kihikihi, a car smashed into a powerpole in wet, slippery conditions at 9.10am bringing down powerlines.

In Thames, a vehicle came unstuck on the Kopu Bridge just after midday and a short time later a car rolled on SH26 at Motumaoho.

A car was also trapped when floodwaters breached road level on SH2 through the Karangahake Gorge around the time it was closed.

Phillips said water was over the road in a number of places to a depth of up to one metre when the rescue was made.

Waikino Tavern publican Naomi Greener said she hadn't seen flooding that bad since 2005 and was hopeful it wouldn't get as bad as the floods of 1981 when the building was breached and others washed away.

Her 6-year-old son had packed all his toys just in case the family had to evacuate. And Greener was preparing to sandbag if the river kept rising with the tide.

"When they were about to close the road we had a couple of four-wheel-drives that pushed through. That said, there were people stranded in the gorge. We rang up and they sent a fire truck through to guide them out."

Farmers were advised to move stock to higher ground as the heavy rain persisted throughout yesterday.

Waikato Federated Farmers president James Houghton said working in the bitter conditions was "bloody miserable".

"We had a few miserable sick calves that came in the morning that needed a bit of TLC during the day.

"Most farmers are kicking off calving and hopefully there aren't too many lambs around at this stage."