Frost Risk

Ground frost forms when the ground surface cools below 0°C. This can happen even when the screen temperature (1.2m) reads +2–3°C. Open paddocks, still air, and clear skies maximise radiative cooling. Hollow ground and river valleys are coldest.

The coastal location moderates frost risk compared with the Tokomairiro valley inland. Sea surface temperatures rarely allow air to fall below -2°C at the coast. The most severe frosts follow extended anticyclones in June–August with clear skies and no onshore breeze.

Watch for: clear skies after 6pm, dewpoint below +2°C, winds calm or less than 5 km/h, and no cloud cover. When the overnight minimum is forecast below +2°C, ground frost is likely.

Typically November through March at Toko Mouth, though frosts as late as early November and as early as late April can occur. The frost-free window averages around 200 days per year on the coast.