Residents in some parts of Horowhenua are being given sandbags in case flooding threatens their properties.
Photo: RNZ / Rebekah Parsons-King
Motorists in Levin, Shannon and Foxton are also being urged to stay off the roads because of heavy rain.
Horizons Regional Council staff are currently monitoring Manawatū River levels with predictions signalling the possible opening of the Moutua floodgates mid-morning tomorrow.
Acting river management group manager Craig Grant said that a significant amount of rain has fallen over the region this weekend, in particular for the Tararua, Manawatū and Horowhenua districts.
"The Manawatū River is predicted to peak at 8.35 metres tomorrow morning. Should the peak reach 8.6 metres, point 25m above current predictions, this would trigger an opening of the Moutoa gates sometime around mid-morning," Grant said in a statement on the council's website.
He said council staff will be at the Moutua gates site from 6am tomorrow to open the gates if required.
Staff are contacting landowers within the Moutua gates area to ensure they are prepared.
The Horowhenua District Council is also strongly urging Levin, Shannon and Tokomaru residents connected to town water to conserve it and reduce wastewater, as the rain is putting the treatment plant under pressure.
Heavy rain in the lower North Island has already caused surface flooding, slips and road closures.
There is flooding at Levin and a section of State Highway 1 had to be closed when underground pipes exploded and blew open a manhole cover.
There are reports that the Ōhau River near Levin has overflowed its banks.
The Akatarawa Road is closed and there are some minor slips on State Highway 2 over the Remutaka Hill.
Further north, Tairāwhiti Civil Defence is optimistic the region will not get a repeat of last weekend's downpour.
Emergency manager Ben Green said the wet-weather system appears to have hit further south.
Heavy rain warnings are also in place for the Bay of Plenty eastern ranges, Tongariro National Park, Mount Taranaki and the Tararua Range.
Plea to conserve water
Meanwhile, residents of Greytown and Featherston have been asked to conserve water until further notice to prevent supply problems as the area is hit by heavy rainfall.
Wellington Water said that the rain and high river levels are resulting in cloudy water getting into the bores supplying the towns.
Chief advisor for drinking water Laurence Edwards said this is similar to the events last week which caused unexpected interruption to the supply.
He said if residents can limit water use as much as possible, this will prevent it from happening again.