Severe Weather Outlook

Issued: 10:25am Friday 15 May 2026

Valid Sunday 17-May-2026

The ridge of high pressure persists over the South Island, while a southeast flow covers the North Island.

There is minimal risk of severe weather.

Valid Monday 18-May-2026

The ridge of high pressure extends across southern and central New Zealand, while a southeast flow covers northern New Zealand.

There is minimal risk of severe weather.

Valid Tuesday 19-May-2026

The ridge of high pressure persists across southern and central New Zealand, while an easterly flow covers northern New Zealand.

There is minimal risk of severe weather.

Valid Wednesday 20-May-2026

The ridge retreats eastwards, with a north to northeast flow across New Zealand. A front approaches the lower South Island from the Tasman Sea late in the day.

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, 15-May-2026

Issued: 7:19am Friday 15 May 2026

There is minimal risk of thunderstorms or significant convection during this period.



Valid to Noon Saturday, 16-May-2026

Issued: 8:15am Friday 15 May 2026

There is minimal risk of thunderstorms or significant convection during this period.



Valid to Midnight Saturday, 16-May-2026

Issued: 8:17am Friday 15 May 2026

There is minimal risk of thunderstorms or significant convection 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.