Te Kuiti - Extended

Issued 03 March 2025

March 2025 Outlook

February 2025 - A dry end to summer

February saw high pressure dominate the local weather maps, leading to increasing soil moisture deficits across the country with pasture growth stunted considerably for most regions. A medium-scale adverse drought was declared for Taranaki on the 27th, with New Plymouth sitting at 35% of the average yearly rainfall to-date and Hawera seeing a mere 8.4mm last month.

It’s not just the Taranaki region experiencing a lack of rainfall. The upper North Island experienced an abnormally dry February with Auckland and Dargaville recording less than 20% of their average February monthly rainfall accumulation, and yearly totals well below where they normally sit. In fact, most of the North Island experienced very little rainfall this past month, with Hamilton and Palmerston North also well below normal.

Dry conditions abounded across the South Island as well, assisted by abundant sunshine and warmer-than-average temperatures for this time of year. Mount Cook has recorded only 29% of their average rainfall to-date, while Haast dropped to only 20%. This has increased pressure on hydro-producing lakes and could impact irrigation if this trend continues, though a slight shift in the weather pattern is expected we head into March.

Climate Drivers - La Niña signal eases, but keep a keen eye to the north from late March

El Niño-Southern Oscillation (ENSO) sea surface temperatures have warmed slightly to neutral territories, while atmospheric conditions are now exhibiting more La Niña-like characteristics. Whilst it is now unlikely a La Niña will be declared, New Zealand may still favour northerly lows and warm, humid flows during the last part of March.

Both the Southern Annular Mode (SAM) and Tasman Sea Index (TSI) should trend positive (more settled and dry) from later this week through next week as high pressure builds. Another Madden-Julian Oscillation (MJO) pulse is expected late March, with an increased risk for tropical development. Whether any of these may spread southwards towards New Zealand will depend on how quickly high pressure eases and moves eastwards, so keep your eyes northwards.

Abundant sunshine last month allowed sea surface temperatures to rise rapidly, particularly near the South Island and western North Island where anomalies are now 1-2C above normal. This warming trend may continue through March, with hints of a marine heat wave developing which could add fuel and strength to any incoming weather systems across the latter part of March.

March 2025 Outlook - An active start, but high pressure returns

A cold front brings modest westerly rain and a cooler reprieve to the country this week, followed by a showery onshore flow across eastern regions that may deliver a decent chunk of this months’ rainfall in those eastern regions. High pressure is then forecast to return, with high confidence of warmer-than-average temperatures and a general drying trend country-wide through at least mid-month.

The persistent high pressure shows signs of weakening during the third week of March, with the odd system becoming more likely to spread across the country with modest rainfall, though most of New Zealand is likely to remain drier-than-average. Temperatures are also expected to remain above normal, with increasing soil moisture deficits and drying soils looking likely to persist.

The final week of March shows slightly more promise for rainmakers. High pressure should ease and move eastwards, with the Southern Ocean and south Tasman Sea showing signs of reawakening, though western regions of the North Island may see the dry weather hold on a bit longer through the end of the month. Saying that, the tropics may become more active towards the end of March, but any southward progression towards the country will be highly dependent on how quickly the high pressure departs.

While this may not be the weather forecast that everyone desires, a quick look into early April provides a glint of hope for a return to more frequent weather systems.

Bottom Line

A cold front delivers westerly rain followed by showers in the east this week, then building high pressure brings largely dry conditions across the country for most of March.