Thunderstorm Outlook
Issued at 6:59am 14/12/2025
Valid from 6:59am 14/12/2025 to 1:00am 15/12/2025
There is minimal risk of thunderstorms or significant convection during this period.
Issued at 8:02am 14/12/2025
Valid from 1:00am 15/12/2025 to 1:00pm 15/12/2025
There is minimal risk of thunderstorms or significant convection during this period.
Issued at 8:48am 14/12/2025
Valid from 1:00pm 15/12/2025 to 1:00am 16/12/2025
Monday afternoon and evening a front moves northeast over the central South Island, followed by an unstable showery air-mass. During the afternoon and evening there is a low risk of thunderstorms with heavy rain for the far south of Westland, Fiordland, Southland and Clutha. The risk increases to moderate in the evening and at night for Fiordland and Stewart Island as indicated on the chart and those storms may be accompanied by heavy rain, 10 to 20 mm/h, small hail and strong wind gusts of around 90 km/h. There is minimal risk of thunderstorms or significant convection elsewhere in New Zealand 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.
