Severe Weather Outlook

Issued: 1:57pm Sunday 31 Aug 2025

Valid Tuesday 02-Sep-2025

A front moves north over the South Island and the lower North Island followed by a strong southwest flow. There is low confidence of severe southwesterly gales affecting coastal Clutha, Dunedin and North Otago, also Banks Peninsula during the morning and afternoon.

The front also brings significant snow down to 5 to 600 metres over the south of the South Island. While warning amounts are unlikely to accumulate there could be significant disruptions to travel due to snow on roads. Livestock may also be affected by the snow and cold temperatures.

Valid Wednesday 03-Sep-2025

A ridge of high pressure builds over much of the country, but a moist northwesterly flow strengthens over the south of the South Island.

The risk of severe weather is considered minimal.

Valid Thursday 04-Sep-2025

A front moves northeast over the South Island and onto the lower North Island. There is low confidence that severe northwesterly gales will affect Wellington. There is also low confidence that warning amounts of rain will accumulate in Westland and northern Fiordland.

Valid Friday 05-Sep-2025

An unstable west to southwest flow affects New Zealand, bringing rain or showers to western and southern parts of the country.

The risk of severe weather is considered minimal.

Low confidence:

A 20% likelihood (or 1 chance in 5) of a warning being issued.

Moderate confidence:

A 40% likelihood (or 2 chances in 5) of a warning being issued.

High confidence:

a 60% likelihood (or 3 chances in 5) of a warning being issued.

New issues of this forecast are made available on this site at or before 16:30 NZST

Thunderstorm Outlook

Valid to Midnight Monday, 01-Sep-2025

Issued: 8:02pm Sunday 31 Aug 2025

There is a low thunderstorm risk about southern and western coastal areas as fronts move northwards through southern and central New Zealand during the afternoon, as indicated on the chart. In the evening and at night another front approaches the far south of the South Island, and there is a moderate risk of embedded thunderstorms bringing heavy rain (10-15 mm/h), and strong gusts (90 km/h). There is minimal risk of thunderstorms or significant convection elsewhere during this period.



Severe Thunderstorm Criteria

In New Zealand, MetService classifies a thunderstorm as severe if one or more of the following criteria are met:

Heavy rain (from thunderstorms):

Rainfall of 25 millimetres per hour, or more.

Large hail:

Hailstones 20 millimetres in diameter, or larger.

Strong wind gusts (from thunderstorms):

Gusts of 110 kilometres per hour / 60 knots or stronger.

Damaging tornadoes:

Fujita F1 (wind speeds greater than 116 kilometres per hour / 63 knots) or stronger.