Severe Weather Outlook

Issued: 9:38am Saturday 29 Aug 2026

Valid Monday 31-Aug-2026

A strong and unsettled west to southwest flow affects New Zealand.

There is moderate confidence that westerly winds will reach severe gale about the Tararua District and Hawke's Bay south of SH5. There low confidence that severe southwesterly gales will affect southern Southland, Clutha and Dunedin.

Valid Tuesday 01-Sep-2026

Strong southwesterlies gradually ease as a ridge builds from the Tasman Sea. However, a strong southwest flow affects the Chatham Islands and there is a low confidence that southwesterlies could reach severe gale there.

Minimal risk of severe weather elsewhere.

Valid Wednesday 02-Sep-2026

A northwesterly flow strengthens ahead of a front that moves onto the lower South Island in the morning.

There is low confidence that warning amounts of rain will accumulate in Fiordland and Westland. There is low confidence that severe northwest gales will affect Fiordland, Southland, Otago, Canterbury, Wellington, and Wairarapa including the Tararua District as indicated on the chart.

Valid Thursday 03-Sep-2026

A strong northwesterly flow with embedded fronts and troughs affects New Zealand.

There is low confidence that warning amounts of rain may accumulate in Fiordland, Westland, Grey and Buller. There is low confidence that severe northwesterly gales may affect Wairarapa including the Tararua District.

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 Sunday, 30-Aug-2026

Issued: 7:48pm Saturday 29 Aug 2026

Chart reviewed at 7:45pm Saturday and minor changes made to low risk area. A strong cold and unstable southwest flow affects southern Fiordland, Southland and parts of Otago. From afternoon, this risk includes Banks Peninsula too. There is a low risk of squally thunderstorms with small hail wind gusts of 80 to 100 km/h as indicated on the chart. There is minimal risk of thunderstorms or significant convection elsewhere in New Zealand 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.