Thunderstorm Outlook
Issued at 8:06am 20/01/2026
Valid from 8:06am 20/01/2026 to 1:00am 21/01/2026
A very moist, unstable easterly flow affects the upper North Island, bringing rain or showers to many places. There is a general low risk of thunderstorms into the evening from Coromandel Peninsula northwards. This morning and afternoon, however, there is a moderate risk of localised downpours of 25 to 40+ mm/h about Northland, northernmost Auckland and Great Barrier Island. No thunderstorms or significant convection expected elsewhere today. Before dawn and early morning there is a moderate risk of thunderstorms for Northland with heavy rain, 10 to 25 mm/h. There is also a moderate risk of localised downpours bringing 25 to 40 mm/h or possibly more. During the morning this moderate risk of thunderstorms with heavy rain, 10 to 25 mm/h spreads to Auckland north of Auckland City and Great Barrier Island as indicated on the chart. There is also a moderate risk of localised downpours bringing 25 to 40 mm/h or possibly more. A Watch and Warning for heavy rain is in force. No thunderstorms or significant convection is expected in other areas of New Zealand.
Issued at 7:55pm 20/01/2026
Valid from 1:00am 21/01/2026 to 1:00pm 21/01/2026
A very moist tropical air mass moves onto the upper North Island during the first half of Wednesday, bringing rain or showers with possible heavy falls. Severe Weather Warnings and Watches are in force for many areas. There is a low risk of thunderstorms from Coromandel Peninsula northwards, and for the northeast of Northland there is a low risk of localised downpours of 25 to 40 mm/hr in the morning. No thunderstorms or significant convection expected elsewhere during this period.
Issued at 10:18am 20/01/2026
Valid from 1:00pm 21/01/2026 to 1:00am 22/01/2026
The very humid tropical air mass continues spreading southwards across the upper North Island during the second half of Wednesday, accompanied by heavy rain or showers. Severe Weather Warnings and Watches are in force. There is a low risk thunderstorms with heavy rain from about East Cape, Bay of Plenty and Waikato northwards. From Coromandel Peninsula northwards, however, there's a low risk of localised downpours of 25 to 40 mm/hr. No thunderstorms or significant convection expected 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.
