Heavy rain is pounding Canterbury - with people warned to prepare for flooding as stormy weather sweeps the country.
MetService is forecasting 200 to 300 millimetres of rain in the Canterbury High Country and foothills which can be expected to cause some rivers and streams to burst their banks.
Civil Defence is on standby.
Canterbury's emergency management says it has been in contact with all local authorities, and Civil Defence plans are in place for if the weather gets severe.
Meteorologist Tom Adams said an unusual weather pattern has set in.
"We live in the Roaring Forties. Typically we get westerly winds but what we're seeing this weekend is a low pressure system that sits up over the country and doesn't budge.
"There's another low system that sits further east and stops it moving and it just sits there for two to three days."
Adams said this is just the second time a red warning has been issued by MetService.
Heavy rain is the main concern in the eastern South Island this weekend, but gusty winds are also expected.— NIWA Weather (@NiwaWeather) May 29, 2021
From tonight through early Monday, easterly winds may gust near or over 70 km/h at times. Combined w/ heavy rain and soggy ground, downed trees and power cuts may occur. pic.twitter.com/XJaYkY77eM
Adams said the Nelson-Tasman region was hard hit earlier today.
Nelson west of Motueka is under a heavy rain watch until 3am tomorrow.
"We've seen some stations, particularly in the Takaka Hill region, that have seen over 100 millimetres in the last 12 hours."
In the seaside suburb of Sumner in Christchurch, local authorities have delivered sand bags to businesses on the main road in case a combination of king tides and rain sends water through the town centre.
There has been some rain in the area, though not a lot. But one local said they are bracing in case it becomes worse.
There are flooding warning signs on some streets in North Brighton although an RNZ reporter travelling through the area could not see any evidence of flooding so far.
It's an area that often floods and she says that the rain has got heavier since about 6pm.
Why is this event so bad❓— MetService (@MetService) May 29, 2021
A slow moving low dominates the country, blocked from moving off by another old low further east. Loop shows winds approx. 10km up that drive the movement of weather systems, and satellite image then model forecast. https://t.co/Yjbq0jxdqz ^TA pic.twitter.com/oFQ2dmB8AC
Civil Defence agencies in other parts of the South Island are also on standby, and Waka Kotahi the Transport Agency is also prepared for possible flooding.
State Highway 8 between Fairlie and Tekapo is being affected by snow and ice tonight.
Road snowfall warnings remain in place for other South Island passes.
MetService says one to three centimetres of snow is expected to settle near the summit of Arthur's Pass this evening, through to tomorrow morning.
Similar amounts are also expected to settle near the summit of Porters Pass.
Snow warnings have been lifted for Lewis Pass and the Crown Range Road.
Transport Agency spokesperson Tresca Forrester has urged South Islanders to take care on the roads.
"We are resourced up for the weekend and we've put plans in place if we do end up closing roads in particular, putting detours in place if need be. But it's all dependent on how heavy the rain comes and where it comes in. All we can do is be prepared and ready to respond."
The heavy rain in Canterbury is being closely monitored for its effect on the region's rivers.
Shaun McCracken, the flood controller for the area from Hinds to Kaikoura, said rivers of concern include the Ashley, Selwyn, Ashburton, Opihi and Orari rivers along with the tributaries that flow into those rivers.
McCracken said river flows will be highest on Sunday and Monday.
Niwa is forecasting a rapid increase in river flows across Canterbury.
There have been heavy thunderstorms in the upper North and upper South Island today as a series of active fronts and troughs pass over the country.
Earlier today MetService reported 1233 lightning strikes in 120 minutes.
1233 lightning strikes in 120 minutes— MetService (@MetService) May 28, 2021
Here's the latest image from our rain radar, with overlaid lightning data.
Red ❌'s and ⭕'s are cloud to ground and cloud to cloud strikes in the last half hour, with orange, purple, and blue representing older strikes.
National Emergency Management Agency communications manager Anthony Frith said when the rough weather set in, it could be serious.
"This has the poetntial to be quite a serious flooding event for some regions, and people need to take it seriously. Listen to the advice and instructions of their local authorities and local Civil Defence groups, and listen to the radio and other media. It's really important that people stay away from floodwater, please drive only if absolutely necessary."
MetService has also warned that a combination of king tides and strong northwesterlies may bring coastal inundation to Auckland this weekend.
A combination of king tides and strong northwesterlies bring possible coastal inundation to Auckland this weekend.— MetService (@MetService) May 28, 2021
Tides could reach 4.0m causing inundation around low lying coastal areas
Keep up to date with the latest at: https://t.co/Yjbq0jxdqz ^Ash pic.twitter.com/Bf8T3t9knf