More than 55mm of rain has fallen in the garden city in the last 24 hours, setting a new record of 212mm rainfall for the month of July.
The previous record for July was set in 1978 with 199mm.
MetService said Christchurch is "extremely wet" following heavy rain overnight.
The downpour has caused flooding and closed roads across the city.The Avon and Heathcote rivers have both burst their banks in places.
Hadlee Pavilion at Hagley Oval is also flooding, with water coming in at the ground level.
MetService says Christchurch has had its wettest month since records began nearly 80 years ago.
The Avon River has breached its banks along Oxford Tce near Barbadoes St.
Residents near the Port Hills are being urged to watch for rapidly rising streams and rivers, with surface flooding and slips.
The following roads are now closed:
Francis Avenue, from Warrington Street to 40 Francis Avenue
Emmett Street, from Briggs Road to Shirley Road
Carrick Street, from Flockton Street to Aylesford Street
Harrison Street, from Thornton Street to Aylesford Street
State highways
Waka Kotahi NZ Transport Agency is advising travellers in the South Island to check their route before they set off today.
Snow has closed inland passes (Burkes and Lindis, and the road into Aoraki/Mt Cook) in South Canterbury/Otago and flooding has closed SH1 to Blenheim and Picton at Seddon in Marlborough. SH1 is likely to be closed all day at Seddon due to flooding.
It is possible that more highways may be closed due to flooding as the day progresses, says Waka Kotahi Journey Manager Tresca Forrester.
“Please slow down and drive to the conditions if there is surface flooding to avoid making waves. People should expect roads that are open to be slower than usual with damage from last week’s storm creating some slower patches in many places across our network.”
Check what State Highways are open.
Peter Timbs butcher's shop in Edgeware is closed again because of flooding.
City council head of three waters Helen Beaumont said the installation of a pump station to try to fix the problem would cost $15 million to $20 million.
She says that would involve draining the water down Madras St into the Avon.
Meanwhile, a MetService spokesman said the worst of the rain has passed through Christchurch and is heading south.
An associated low to the west of the upper North Island would also move slowly southwards, then weaken and cross the South Island on Wednesday.
A heavy rain warning is in place until 3am on Wednesday morning for Canterbury, south of the Rakaia River with 100 to 130mm of rain expected to accumulate about the foothills, peaking at 10 to 15 mm per hour.
A heavy rain watch is also in place for all of Canterbury from Rakaia River northwards with periods of heavy rain, rainfall amounts may approach warning criteria through to until 6pm on Tuesday.
North Otago could expect up to 130mm of rain to accumulate between 6am today and 8am on Wednesday, especially inland, with peak rates of up to 15mm per hour.
Dunedin residents could expect up to 90mm of rain between 7am today and 9am on Wednesday — again, with peak rates of up to 15mm per hour.
"People are advised to keep up to date with the latest forecasts in case any changes are made, or further areas are added," he said.
MetService has also issued a number of road snowfall warnings from today to tomorrow, including for Lewis Pass from 2pm to 9pm, Arthur's Pass 3pm to 2am, Porter's Pass from 4pm to 1am, Lindis Pass from 8pm to 11pm and the Crown Range Rd from 1am to 4pm.-Additional reporting ODT
