Christchurch is on track to record its driest May in modern history, with only 5.2 millimetres of rain falling on the city so far this month. That total is less than half the previous record of 11.2 millimetres set in 2012, and it sits more than fourteen times below the 76 millimetres the city received in May last year, according to figures reported by RNZ this week.
For a city where the long-term average for May runs at roughly 58 millimetres, the gap is striking. NIWA records show Christchurch typically picks up showers every few days through autumn as fronts roll across the eastern South Island. This year the showers have not arrived. A near-permanent ridge of high pressure has parked itself over Canterbury, blocking rain-bearing systems and leaving the Port Hills hazy with woodsmoke each evening.
MetService said high pressure will hold through Friday and most of Saturday before a low-pressure system finally pushes across the South Island on Sunday. Christchurch itself looks set to stay mostly dry, with only the chance of showers on Monday and Tuesday. That timing matters. If the showers fall short of six millimetres over the remaining days of May, Christchurch will overtake 2012 to claim its driest May on record.
The dry spell is not confined to Christchurch. Below-average rainfall has settled in across the lower North Island and the eastern South Island through May. Farmers across the Canterbury Plains and into North Otago have been topping up troughs from bore water, and autumn pasture growth has slowed in the rain shadow east of the Southern Alps. Soil moisture monitoring stations run by NIWA have been tracking the deficit through the second half of the month.
The other side of the dry pattern is cold. With clear nights and no cloud cover to hold in the day’s warmth, temperatures across the central South Island have plunged well below freezing. The New Zealand Transport Agency has issued a warning for State Highway 8 and State Highway 80 through the Mackenzie Basin, where widespread frosts are expected on Saturday morning. “There is an elevated risk of ice on the roads and bridges on Saturday before rain is expected to arrive for many places on Sunday,” the agency said. Frosts are also forecast on State Highways 7, 73 and 77 through Sunday.
The pattern flips by the weekend. The South Island will see heavy rain in the west on Sunday as a front moves in from the Tasman, followed by scattered rain across the rest of the island. The North Island gets it next. Auckland is forecast to be hit by heavy rain and strong north-easterly winds on Sunday, while the Wellington region has heavy rain pencilled in for Monday. By Tuesday the high-pressure pattern that has dominated late autumn looks ready to break, with most of the country expecting more typical wet, cool conditions.
For Christchurch, the real question is whether the weekend’s rain band can swing far enough east in time, or whether the city ends May with the new record. The May 2012 mark of 11.2 millimetres has stood for fourteen years. To pass it, Christchurch would only need six more millimetres of rain over the next four days. That sounds easily achievable, except that the front responsible for Sunday’s rain in the west is forecast to weaken sharply as it crosses the Alps. Foehn winds are likely to dry it out before it reaches the city, which is the same mechanism that produces nor’wester conditions through summer.
Dry Mays are not unheard of in Christchurch. The city sits in the rain shadow of the Southern Alps and tends to swing from very wet to very dry across autumn, depending on whether prevailing winds come off the Tasman or from the south. What is unusual this year is how long the high-pressure ridge has held in place. Long blocking highs over the South Island have shown up in earlier dry seasons too, including 1972, 1996 and 2012, but the May 2026 pattern has been notably persistent.
It will be several days before NIWA confirms whether the record falls. The agency’s monthly climate summary usually appears in the first week of the following month, drawing on official rainfall stations including Christchurch Airport and the Botanic Gardens. Either way, the dry autumn is already shaping conversations heading into winter. Canterbury’s hydro and agricultural sectors are watching the South Island snowpack closely, and the major skifields are due to open in late June with operators hoping for early winter storms to top up bases.
Forecasters have stopped short of calling the dry pattern unusual in any climate-driven sense. Blocking highs are a normal feature of late autumn in the South Island and the underlying signal so far this year sits within the range of natural variability. What it does mean for households and businesses across the Canterbury Plains is a longer than usual run of fine, cold days, the kind of weather that puts pressure on water tanks in the foothills and rewards anyone who put their woodshed in order back in March.
Have you noticed how dry it has been in your part of the country this autumn? Tell us what you have been seeing in the comments below.
This article was written by AI, briefed to report the facts, hopefully without some of the bias people bring to the job π
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