Evers-Swindell Park in Clive floods, Hawke's Bay Regional Council working to divert river

The regional council is looking to realign the river mouth this afternoon. Photo / Supplied

Flooding near Clive caused by swells narrowing rivermouths downstream prompted the Hawke's Bay Regional Council contractors to open a swollen rivermouth on Tuesday afternoon.

The Evers-Swindell Park and parts of the Hawke's Bay Trails around Waitangi Regional Park flooded on Tuesday morning with high tide, which can affect flows in the Clive River, coming in about 6pm.

Hawke's Bay Regional Council team leader schemes Antony Rewcastle said the flooding was mainly due to the large southerly swells that are narrowing the rivermouth and causing it to run parallel with the beach, meaning water is moving out of the river more slowly than it normally does.

The regional council said on Facebook that river levels were high on the Clive, Ngaruroro and Tūtaekurī rivers.

This prompted it to send in contractors to open the mouth of the rivers using diggers on Tuesday afternoon.

The rivermouth was also being realigned to help with flow out of the river into the sea and reduce water levels back to normal.

The Maraetōtara, Esk, Te Ngarue and Waihoratuna rivermouths have also closed due to a southerly swell and were being closely monitored.

"We haven't been able to open the rivers earlier because of the unsafe swell conditions.

"The [Clive] rivermouth is open, but we are looking to realign it [this afternoon] to improve the flow of water out to the ocean and reduce water levels in the rivers back to normal."

The regional council is looking to realign the river mouth this afternoon. Photo / Supplied

River levels have been high for the past few days.

The Ngaruroro's mouth opened naturally on Friday morning, August 6, at low tide but the Hawke's Bay Regional Council had previously signalled it would send contractors to open it themselves if needed.

High river levels have flooded parts of the Hawke's Bay Trails at Waitangi. Photo / Craig Cooper

It's the latest fallout in Hawke's Bay from Monday's cold snap.

Elsewhere, the roads around the region were on Tuesday slowly returning to normality in the August sunshine.

On Tuesday morning State Highway 5 between Napier and Taupō was open, but the New Zealand Transport Agency was advising motorists to treat the trip with caution.

The Napier-Taihape Road also reopened on Tuesday afternoon.

Snow closed main roads into Hawke's Bay on Monday - SH2 between Gisborne and Wairoa was closed for a short period on Monday evening - and SH5's closure on Monday morning left a dozen trucks stuck.

The winter blast coated the hills around the region in white and hail fell at semi-regular intervals across the twin cities.

The Evers-Swindell Park and rowing club in Clive have flooded. Photo / Hawke's Bay Regional Council

It also brought wind in its icy breath. MetService meteorologist Lewis Ferris said the strongest gust of wind happened between 4am and 5am on Monday at Mahia and measured 152km/h.

Winds reached 83km/h in Napier shortly before 8am and 91km/h in Wairoa just before 10am.

Wednesday is expected to be mainly fine but a shower is possible in the afternoon or evening.

Napier is forecast to reach 16 degrees Celsius, Hastings 17C, Waipukurau 15C and Wairoa 16C.