Thunderstorm Outlook
Issued at 8:02am 31/05/2026
Valid from 8:02am 31/05/2026 to Midnight 31/05/2026
An elevated thunderstorm risk has been assessed as low for western parts of the South Island from Fiordland to western Tasman District. Additionally, a front approaches the far north of Northland later in the day and there is a low risk of thunderstorms from evening. Minimal risk of thunderstorms or significant convection for the remainder of New Zealand.
Issued at 9:13am 31/05/2026
Valid from Midnight 31/05/2026 to Midday 1/06/2026
A front brings heavy rain to the west and north of the South Island. Embedded in this rain band there is a low risk of thunderstorms from western Tasman District to Northern Fiordland. From mid-morning however, the risk is considered moderate for Westland with heavy rain of 20-30 mm/h. Additionally, there is a low risk of thunderstorms for Northland. Minimal risk of thunderstorms or significant convection for the remainder of New Zealand.
Issued at 9:13am 31/05/2026
Valid from Midday 1/06/2026 to Midnight 1/06/2026
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 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 remains low, but there is a moderate risk of downpours from evening with rain rates of 25-40 mm/h. 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.
