Thunderstorm Outlook
Issued at 7:21am 8/06/2026
Valid from 7:21am 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 low risk of thunderstorms for Fiordland and Westland between Doubtful Sound and Haast this morning. There is a moderate risk of thunderstorms about and offshore coastal Clutha this afternoon, and a low risk for Stewart Island, Southland east of Riverton, other parts of 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 from afternoon. There is minimal risk of thunderstorms or significant convection elsewhere in New Zealand today.
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.
