Thunderstorm Outlook
Issued at 8:19am 7/08/2026
Valid from 8:19am 7/08/2026 to Midnight 7/08/2026
A front brings rain to the west of the South Island, and instability increases in the southwest of the Island following the front. Mainly about areas near the coast, there is an associated moderate risk of thunderstorms in Fiordland and southern Westland this afternoon, evening and at night, while about central and northern Westland and southern Buller districts, the risk of thunderstorms is considered low during this time. These thunderstorms if they occur could bring rain with intensities of 10 to 20 mm/h, and about Fiordland and southern Westland small hail. There is minimal risk of thunderstorms or significant convection elsewhere during this period.
Issued at 8:21am 7/08/2026
Valid from Midnight 7/08/2026 to Midday 8/08/2026
A front remains slow-moving over the west of the upper South Island during the first half of Saturday, bringing rain and a low risk of thunderstorms for coastal parts of western Tasman and the Buller District. Further south, cold temperatures aloft and embedded troughs bring periods of heavy showers and there is a moderate risk of thunderstorms for Fiordland before dawn and during the morning. These thunderstorms if they occur could bring rain with intensities of 10 to 20 mm/h, and small hail. 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.
