Severe Weather Outlook

Issued: 10:40am Saturday 20 Jul 2024

Valid Monday 22-Jul-2024

South to southwest winds spread over the country with periods of rain or showers for many places, especially about the west of the North Island. However, there is minimal risk of warnings being issued.

Valid Tuesday 23-Jul-2024

A southwest flow lies over the country, with showers in some places. There is minimal risk of severe weather.

Valid Wednesday 24-Jul-2024

A weak ridge of high pressure is forecast to spread across New Zealand, with minimal risk of severe weather.

Valid Thursday 25-Jul-2024

The ridge of high pressure moves slowly northwards as a front approaches the South Island. The front is expected to bring rain and strong northwesterlies to Fiordland, but at this stage it is considered unlikely that warnings will be needed.

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 Saturday, 20-Jul-2024

Issued: 7:18am Saturday 20 Jul 2024

An unstable northwest flow affects the South Island this morning and afternoon. There is a low risk of thunderstorms this morning and early afternoon for areas from central Westland to northern Fiordland. No thunderstorms or significant convection expected in other areas of New Zealand during this period.



Valid to Noon Sunday, 21-Jul-2024

Issued: 10:24am Saturday 20 Jul 2024

A frontal system from over the Tasman Sea is expected to move onto Northland Sunday morning. There is an associated moderate risk of thunderstorms developing in Northland during the morning. These thunderstorms are likely to bring localised heavy rain with intensities of 10 to 25 mm/h and strong wind gusts of 80 to 100 km/h. A lower risk of thunderstorms extends through Auckland and Coromandel Peninsula to Waikato and Waitomo. No thunderstorms or significant convection expected in other areas of New Zealand during this period.



Valid to Midnight Sunday, 21-Jul-2024

Issued: 10:39am Saturday 20 Jul 2024

The frontal system moves over northern New Zealand during the course of Sunday. There is an associated moderate risk of thunderstorms in Northland, Auckland, Coromandel Peninsula, Waikato, Waitomo, and Taranaki. These thunderstorms are likely to bring localised heavy with intensities of 10 to 25 mm/h, and for Northland, Auckland, Waikato and Coromandel Peninsula strong winds gusting 80 to 100 km/h. A lower risk of thunderstorms extends across the Bay of Plenty, Taupo and Taumarunui. 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.