Winter 2025 is shaping up to be unusually warm across New Zealand, with NIWA forecasting above-average air and sea temperatures, reduced frost frequency, and ongoing marine heatwave (MHW) conditions. While these trends bring extended opportunities for boating, they also raise the likelihood of heavy rain events, shifting wind patterns, and unpredictable marine conditions.
Warmer temperatures, fewer cold snaps
Air temperatures are expected to be above average in all regions, especially in the upper North Island and much of the South Island. Frosts and cold spells will still occur but will be less frequent. For boaties, this means more comfortable conditions through winter—fewer icy mornings and more days suitable for time on the water.
Persisting marine ‘heatwaves’
Sea surface temperatures remain well above normal across most of the country, with marine heatwave conditions persisting on both islands’ western and northeastern coasts. These warmer seas could extend the inshore fishing and diving season, although the risk of fog and sudden weather changes remains high due to temperature contrasts between sea and air.
Rain and weather volatility
Higher pressure east of New Zealand is expected to drive more northeasterly winds, later shifting to northwesterlies. These wind patterns, combined with low pressure systems from the tropics, may bring periods of heavy rain, especially in Northland, Auckland, and the Bay of Plenty. Rainfall is likely near or above normal in most areas, and boaties should stay alert for fast-changing weather, particularly following tropical rain events.
Lingering La Niña effects
Although ENSO conditions are officially neutral, residual La Niña signals remain, meaning some easterly or northeast weather patterns may continue. The result is less winter stability than usual, with frequent regional variations and isolated extreme events still possible.
Regional summary for boaters
Upper North Island
Very warm and wetter than usual. Watch for fog and heavy rain spells.
Central North Island to Wellington
Mild with variable rainfall. Inland boating areas may see clearer conditions but still need caution.
East Coast North Island
Slightly more stable. SSTs near normal, but northeasterlies could complicate coastal conditions.
Top of South Island
Warmer than usual with mixed rainfall. Northwesterlies later in winter may impact Cook Strait passages.
West/South South Island
Warm seas and air but prone to swell and weather swings.
Canterbury/East Otago
Stable and mild, with near-normal rain. Safer cruising but still watch the wind shifts.
Takeaways
Expect more fishable, dive-worthy, and cruise-ready days—but don’t be lulled by the mildness. Fog, subtropical lows, and rain bursts can quickly change conditions. Winter 2025 offers more time on the water, but it also calls for extra vigilance and regular forecast checks. Warm doesn’t mean calm—but it does mean more boating is on the table if you stay weather-aware.
