Thunderstorm Outlook
Issued at 7:58am 12/05/2025
Valid from 7:58am 12/05/2025 to Midnight 12/05/2025
Fronts are expected to be approaching the south of the South Island late today. There is a low risk of thunderstorms about southern Fiordland and parts of Stewart Island at night. No thunderstorms or significant convection expected elsewhere during this period.
Issued at 8:34am 12/05/2025
Valid from Midnight 12/05/2025 to Midday 13/05/2025
A front and preceding trough move northwards onto the South Island during Tuesday morning. There is a low risk of thunderstorms for Fiordland and the very far south of the Westland District as indicated on the chart. No thunderstorms or significant convection expected elsewhere during this period.
Issued at 8:35am 12/05/2025
Valid from Midday 13/05/2025 to Midnight 13/05/2025
No thunderstorms or significant convection expected 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.
