Severe Weather Outlook

Issued: 9:01am Friday 18 Jul 2025

Valid Sunday 20-Jul-2025

A showery southerly flow affects the North Island, while a ridge of high pressure covers the South Island.

There is minimal risk of severe weather.

Valid Monday 21-Jul-2025

A showery southerly flow affects the North Island. A ridge of high pressure over the South Island weakens, while a trough brings showers to the south of the South Island.

There is minimal risk of severe weather.

Valid Tuesday 22-Jul-2025

A ridge of high pressure builds over southern and central New Zealand, while a showery southerly flow over the North Island eases.

There is minimal risk of severe weather.

Valid Wednesday 23-Jul-2025

A large ridge of high pressure covers all of New Zealand.

There is minimal risk of severe weather.

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 Friday, 18-Jul-2025

Issued: 7:23am Friday 18 Jul 2025

A front is expected to move north over the southwest of the South Island from this evening, and there is an associated low risk of thunderstorms for Fiordland and Stewart Island. No thunderstorms or significant convection expected in other areas of New Zealand.



Valid to Noon Saturday, 19-Jul-2025

Issued: 9:14am Friday 18 Jul 2025

The front continues to move northwards over the South Island Saturday morning, and there is an associated low risk of thunderstorms for coastal areas from Fiordland to Buller. No thunderstorms or significant convection expected in other areas of New Zealand.



Valid to Midnight Saturday, 19-Jul-2025

Issued: 9:14am Friday 18 Jul 2025

The front moves onto western areas of central New Zealand during Saturday afternoon and evening. There is a low risk of thunderstorms for coastal areas of Buller and western Tasman in the afternoon and evening, and for southern Taranaki from evening. No thunderstorms or significant convection expected in other areas 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.