Thunderstorm Outlook
Issued at 7:15am 23/09/2026
Valid from 7:15am 23/09/2026 to Midnight 23/09/2026
A trough followed by a southeast wind change moves over the northeast of the North Island this afternoon, and there is an associated low risk of thunderstorms for the far north of Gisborne/Tairawhiti and coastal parts of Bay of Plenty, as indicated on the chart. There is minimal risk of thunderstorms or significant convection elsewhere today.
Issued at 8:10pm 23/09/2026
Valid from Midnight 23/09/2026 to Midday 24/09/2026
A front embedded in a westerly flow is forecast to move onto the south of the South Island from the Tasman Sea during Thursday morning. There is a low risk of thunderstorms for Fiordland south of George Sound and Stewart Island throughout the morning. After dawn, there is also a low risk of thunderstorms for Fiordland from George Sound northwards, and for coastal parts of Southland and Clutha, as depicted on the chart. There is minimal risk of thunderstorms or significant convection elsewhere during this period.
Issued at 8:13pm 23/09/2026
Valid from Midday 24/09/2026 to Midnight 24/09/2026
,A front embedded in a westerly flow is forecast to move slowly northwards over southern New Zealand during the latter half of Thursday. There is a low risk of thunderstorms for Fiordland and Westland south of Haast, which spreads northwards to the glaciers from evening, as depicted on the chart. During the afternoon, there is also a low risk of thunderstorms for Stewart Island, Southland, Clutha, Dunedin, Central Otago south of Alexandra, North Otago, and the Canterbury Plains from Timaru southwards. There is minimal risk of thunderstorms or significant convection elsewhere 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.
