Thunderstorm Outlook
Issued at 7:51am 16/09/2026
Valid from 7:51am 16/09/2026 to Midnight 16/09/2026
A front moves onto Westland this afternoon, and there is an associated low risk of thunderstorms for Westland, Grey and the Paparoa Range this evening and at night as indicated on the chart. There is minimal risk of thunderstorms or significant convection elsewhere during this period.
Issued at 7:08pm 16/09/2026
Valid from Midnight 16/09/2026 to Midday 17/09/2026
A front clears the northwest of the South Island before dawn, and there is an associated low risk thunderstorms for far northern Westland, Grey, Buller and western Tasman. Another front approaches the far south of the South Island late morning, and along with cooling temperatures aloft, there is a low risk of thunderstorms from late morning for southern Fiordland, coastal Southland and Stewart Island as indicated on the chart. There is minimal risk of thunderstorms or significant convection elsewhere during this period.
Issued at 9:56am 16/09/2026
Valid from Midday 17/09/2026 to Midnight 17/09/2026
A low and frontal system moves onto the upper North Island during the second half of Thursday. There is a broad low risk of thunderstorms from northern Taranaki and coastal Waitomo to Northland, across to Coromandel Peninsula for the whole period, then spreading into coastal parts and the eastern ranges of Bay of Plenty during the evening. However, for northern and eastern parts of Northland in the evening and at night, there is a low risk of localised downpours producing rainfall rates of 25 to 40 mm/h. A front moves moves eastwards across the far south of the South Island during the afternoon with cold temperatures aloft. There is a low risk of thunderstorms for central and southern Fiordland, southern Southland and Clutha, however for the southeast of Southland and Clutha, the risk is considered moderate as indicated on the chart. These thunderstorms may be accompanied by heavy rain 10 to 15 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.
