All roads in and out of Wanganui are closed due to severe weather conditions.
Flooding, slips and fallen trees have closed SH3 Whanganui to Bulls, SH4 Whanganui to Raetihi SH3 Patea to Hawera, SH1 Bulls to Hunterville, SH54 Vinegar Hill to Cheltenham, Whanganui River Rd, Mangamahu Rd, Waitotara Valley Rd, Anzac Pde between Portal St and Georgetti Rd, and numerous other urban roads.
People have been evacuated in parts of Putiki, Wanganui East, Aramoho and Brunswick, and a Red Cross evacuation centre has been set up at St Paul's Church in Guyton St.
Wanganui District Council Civil Defence is asking people to stay indoors and not travel unless they absolutely have to.
"We are advising people to keep away from floodwaters, which may be contaminated with sewerage," spokeswoman Cass Alexander said.
There have also been widespread power outages throughout the district, including outages to about half of the council's 24 pump stations.
"We don't have any information available about when the power is likely to be back on, but in the mean time we have reduced the water pressure at the Kai Iwi bore and we are asking people to conserve water," Ms Alexander said.
Ms Alexander said the Matarawa Stream in Wanganui East is rising rapidly, which will cause flooding and sewerage contamination in properties in the Anzac Parade and Nile Street area. The Red Cross is talking to residents in this area.
The Whanganui River is currently at 12.5m at Pipiriki, and the peak is expected to reach Wanganui around 6am on Sunday.
Brenda Kidd, who lives in Purua St, said water running down her street had lifted up the road seal, and slips had blocked the road for some time, although they were able to get out now.
"The kids are making cupcakes in case the power goes out later - we've got soup going in the crock pot, the fire roaring, and we're just going to hunker out," Ms Kidd said.