Thunderstorm Outlook
Issued at 7:48am 20/02/2026
Valid from 7:48am 20/02/2026 to 1:00am 21/02/2026
A series of weak fronts move northwards over the South Island today, bringing brief rain or showers to many areas. There is a low risk of thunderstorms for the Grey District and northern Westland this morning, and for southern and eastern parts of the South Island this morning and afternoon, as depicted on the chart. However, for Westland south of Harihari, Fiordland, and coastal Southland (including Stewart Island) there is a moderate risk of thunderstorms this morning. Any thunderstorms that occur will likely be accompanied by brief heavy rain with intensities of 5 to 15 mm/h and small hail. There is also a moderate risk of thunderstorms for North Otago, the Canterbury Plains, Christchurch, and Banks Peninsula from late morning until late afternoon. Thunderstorms that occur here will generate localised heavy rain up to 20 mm per hour, and possibly strong wind gusts up to 100 km/h and hail 10 to 20 mm in diameter. There is minimal risk of thunderstorms or significant convection elsewhere in New Zealand today.
Issued at 9:40am 20/02/2026
Valid from 1:00am 21/02/2026 to 1:00pm 21/02/2026
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.
