Thunderstorm Outlook
Issued at 1:57pm 8/06/2026
Valid from 1:57pm 8/06/2026 to Midnight 8/06/2026
A front moves northwards over southern and central New Zealand today, followed by a cold and showery southwest flow. There is a moderate risk of thunderstorms about and offshore coastal Clutha and Southland east of Riverton including Stewart Island this afternoon, and a low risk for other parts of Southland, Clutha, and southern parts of Dunedin, as indicated on the chart. Any thunderstorms that occur here will be embedded within a strong southwesterly flow, and will be accompanied by squally gusts of 90 to 110 km/h, and small hail. Also, although not shown on the chart, there is a low risk of thunderstorms for the Chatham Islands. There is minimal risk of thunderstorms or significant convection elsewhere in New Zealand today.
Issued at 7:22pm 8/06/2026
Valid from Midnight 8/06/2026 to Midday 9/06/2026
There is minimal risk of thunderstorms or significant convection during this period. Reviewed at 7:20pm Monday - no changes. Although not drawn on the chart, there is a moderate risk of squally thunderstorms for the Chatham Islands during Tuesday morning. Any thunderstorms that occur there will be embedded within a strong southwesterly flow, and will be accompanied by squally gusts of 90 to 110 km/h, and small hail.
Issued at 8:23am 8/06/2026
Valid from Midday 9/06/2026 to Midnight 9/06/2026
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 25mm/h, or more.
Large hail:
Hailstones 20mm in diameter, or larger.
Strong wind gusts (from thunderstorms):
Gusts of 110km/h (60 knots) or stronger.
Damaging tornadoes:
Fujita F1 - i.e. wind speeds greater than 116km/h (63 knots) or stronger.
Note: some tornadic systems such as funnel clouds, waterspouts and small land-based tornadoes are possible with thunderstorms that may not be classified as severe.
