Thunderstorm Outlook
Issued at 7:35am 21/07/2026
Valid from 7:35am 21/07/2026 to Midnight 21/07/2026
A weak front moves north over the south of the South Island Tuesday afternoon and evening. In the afternoon, evening and at night there is a low risk of thunderstorms with heavy rain for Fiordland and Stewart Island. In the evening and at night there is a low risk of thunderstorms with heavy rain for the far south of Westland as indicated on the chart. There is minimal risk of thunderstorms or significant convection elsewhere during this period.
Issued at 7:24pm 21/07/2026
Valid from Midnight 21/07/2026 to Midday 22/07/2026
A weak front moves north over the west of the South Island Wednesday morning. There is a low risk of thunderstorms from northern Fiordland to Grey, as indicated on the chart. The risk in northern Fiordland eases before dawn. There is minimal risk of thunderstorms or significant convection elsewhere during this time.
Issued at 7:27pm 21/07/2026
Valid from Midday 22/07/2026 to Midnight 22/07/2026
There is minimal risk of thunderstorms or significant convection 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.
