Severe Weather Outlook

Issued: 8:49am Saturday 18 Jul 2026

Valid Monday 20-Jul-2026

A trough of low pressure moves north over central and northern New Zealand. A ridge of high pressure builds over the country to the south of the trough

There is minimal risk of severe weather.

Valid Tuesday 21-Jul-2026

The trough of low pressure becomes slow moving across the north of the North Island. A front over the south Tasman Sea moves onto the south of the South Island later in the day.

There is minimal risk of severe weather.

Valid Wednesday 22-Jul-2026

A front over the South Island becomes slow moving and weakens. A westerly flow develops over the North Island.

There is minimal risk of severe weather.

Valid Thursday 23-Jul-2026

A frontal rain-band over the Tasman Sea moves onto the South Island. Northwesterlies strengthen over central New Zealand ahead of the front.

Associated with the frontal rain-band, there is low confidence for warning amounts of rain in Fiordland and the south of Westland.

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, 19-Jul-2026

Issued: 7:46pm Saturday 18 Jul 2026

Chart reviewed at 7:45pm Saturday and low risk area extended to cover more of Buller. A trough affects the Buller and Tasman Districts from afternoon and there is a low risk of thunderstorms as indicated on the chart. Minimal risk of thunderstorms or significant convection for the rest of New Zealand.



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.