Thunderstorm Outlook
Issued at 7:23am 19/06/2026
Valid from 7:23am 19/06/2026 to Midnight 19/06/2026
A northwesterly flow covers the South Island today, with an embedded front expected to move onto Fiordland tonight. There is a low risk of thunderstorms with heavy rain about the fiords of central and southern Fiordland from late afternoon, then about other parts of Fiordland, southern Westland and Stewart Island at night. There is a minimal risk of thunderstorms or significant convection over the remainder of New Zealand.
Issued at 7:59am 19/06/2026
Valid from Midnight 19/06/2026 to Midday 20/06/2026
The front moves northwards across Fiordland and Westland with heavy rain, then followed by showery northwesterlies. There is a low risk of thunderstorms from the Grey and Westland Districts to Fiordland and Stewart Island, including the headwaters of Otago and Canterbury. The risk of thunderstorms is considered moderate however, from central Fiordland to South Westland before dawn and in the early morning. These thunderstorms may produce localised rainfall rates of 15 to 25 mm/h. There is a minimal risk of thunderstorms or significant convection over the remainder of New Zealand.
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.
