Thunderstorm Outlook
Issued at 8:09pm 31/05/2026
Valid from 8:09pm 31/05/2026 to Midnight 1/06/2026
Chart reviewed at 8:05pm Sunday and the risk of thunderstorms in Northland increased to moderate from evening. The heavy rain for the west and north of the South Island continues for most of the second half of Monday as does the low risk of embedded thunderstorms. However, the risk is considered moderate for Westland south of Hokitika during the afternoon and evening, with heavy rain of 20-30 mm/h. A front moves over Northland late in the day and atmosphere gradually becomes more unstable. The risk of thunderstorms is low during the afternoon but increases to moderate in the evening, but there is also moderate risk of downpours from evening with rain rates of 25-40 mm/h. A low risk of thunderstorms spreads south into Auckland and northern Coromandel Peninsula during the evening. Minimal risk of thunderstorms or significant convection for 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.
