Thunderstorm Outlook
Issued at 8:01am 11/08/2026
Valid from 8:01am 11/08/2026 to Midnight 11/08/2026
There is minimal risk of thunderstorms or significant convection during this period.
Issued at 9:24am 11/08/2026
Valid from Midnight 11/08/2026 to Midday 12/08/2026
A front moves onto Northland overnight and moves slowly southwards. From about dawn onwards there is a low risk of thunderstorms as indicated on the chart. These storms could bring heavy rain of 10-25 mm/h with or without lightning.
Issued at 9:26am 11/08/2026
Valid from Midday 12/08/2026 to Midnight 12/08/2026
The front continues to track southwards over Northland during the second half of Wednesday. The airmass associated with the front is very warm and moist, especially for late winter. There is a low risk of thunderstorms for northern and eastern parts of Northland in the afternoon and evening. These storms could bring downpours (low risk) of 25-40 mm/h with or without lightning. The risk the extends into the northern parts of the Hauraki Gulf and over Great Barrier Island later in the evening and at night as indicated on the chart.
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.
