Peter Meecham/Stuff
Heavy rain flooded low-lying roads and driveways along the Heathcote River on July 21.
Heavy rain warnings and watches have been issued for much of the South Island’s east coast from late Monday into Wednesday.
There are also road snowfall warnings in place for mountain passes including Lewis, Arthur’s, Porters, Lindis and the Crown Range.
A front, which is already causing flooding, road closures and power outages in parts of Northland and Auckland, is making its way south and is expected to hit the South Island on late Monday.
MetService has issued a heavy rain warning for Canterbury, south of the Rakaia River, North Otago and Dunedin. It is predicting 100 to 130 millimetres of rain about the Canterbury foothills and inland Otago and lesser amounts elsewhere.
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The heavy rain was expected in the 26 hours between 1am Tuesday and 3am Wednesday in Canterbury and from 6am Tuesday to 8am Wednesday in Otago.
At the peak the rain would fall at a rate of about 10 to 15mm per hour.
The rain could cause streams and rivers to rise rapidly in both regions, MetService warned. Surface flooding and slips were also possible and driving conditions could be hazardous.
A heavy rain watch has been issued for Canterbury, north of the Rakaia River, for the 18 hours from midnight Monday to 6pm Tuesday.
Roads became rivers along the Heathcote River on Thursday, July 21.
MetService has not indicated how much rain could fall in this area, but warned people to expect periods of heavy rain that may approach warning criteria.
The criteria for a rain warning was for widespread rainfall greater than 50mm in six hours or 100mm in 24 hours.
Christchurch is on track to experience its wettest July on record, after already receiving 157mm of rain this month, well over double the monthly average of 61mm.
The wettest July was recorded in 1977 when 180.8mm of rain fell.
PETER MEECHAM/STUFF
Heavy rain has caused flooding around the Heathcote River in Christchurch.
No rain warning was issued by MetService for Christchurch last week when 44mm of rain fell in the 24 hours to 2pm on Thursday, causing surprise flooding in low-lying areas after the Ōpāwaho/Heathcote and Ōtākaro/Avon rivers broke their banks in sections.
Several cars were water logged, especially those parked next to the rivers and people were stuck in their homes, unable to get out of their flooded driveways.
Heavy rain was also expected in Marlborough from 8pm Monday until noon on Tuesday. The rainfall could exceed warning criteria in places, especially about the Kaikōura Ranges.
Dunedin was expected to experience periods of heavy rain (between 60 and 90mm) between 7am Tuesday and 9am Wednesday.
Heavy rain was predicted for the Tasman district west of Motueka from 3pm Monday until 9am Tuesday. About 80mm to 120mm of northeasterly rain could fall, especially about the ranges.
MetService has forecast 1 to 3 centimetres of snow above 900 metres on the Lewis Pass between 2pm and 9pm Monday. Between 2cm and 5cm was expected on Arthur’s Pass and Porters Pass from Monday afternoon until the early hours of Tuesday.
About 10 to 15cm of snow was forecast above 800m on Lindis Pass from 8pm Monday until 11am Tuesday.
The Crown Range Rd could also expect 5 to 10cm of snow above 800m from 1am Tuesday until 2pm the same day.