Thunderstorm Outlook
Issued at 8:32pm 5/09/2026
Valid from 8:32pm 5/09/2026 to Midnight 6/09/2026
A warm front associated with a complex low pressure system, moves onto the northwest of the South Island during the second half of Sunday. There is a low risk of thunderstorms for a time for northwest Tasman, Buller, Grey and far northern Westland from Sunday late afternoon until late evening. 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.
