Issued at 7:52am 18/09/2025

Valid from 7:52am 18/09/2025 to Midnight 18/09/2025

Several fronts are moving northeast across the country. Cool temperatures in the upper atmosphere are making conditions unstable in many places. There is a generally low risk of thunderstorms in many western areas during the day from Waitomo southwards. For Waikato, Auckland, Northland, northern Coromandel Peninsula and eastern Bay of Plenty there is a low risk of thunderstorms this afternoon and evening. For eastern areas from Clutha to Wairarapa, also Wellington, a low risk of thunderstorms spreads northwards from this afternoon, reaching the North Island this evening. There is also a low risk of thunderstorms about the Chatham Islands this afternoon. For northern Fiordland and southern Westland, the risk of thunderstorms is moderate this morning. For the rest of Westland, Grey and Buller, the risk of thunderstorms is moderate this morning and afternoon. About western Tasman there is a moderate risk of thunderstorms this afternoon and evening and for Taranaki, coastal Whanganui, Manawatu, Horowhenua and much of Kapiti the risk of thunderstorms is moderate this evening and tonight. For these areas the thunderstorms may bring localised heavy rain with intensities of 5 to 15 mm per hour, strong wind gusts of 90 to 100 km/h in the south and 80 to 90 km/h from central Westland northwards. Small hail is possible about the North Island areas, and hail of 5 to 10 mm in diameter is possible for the South Island areas. There is also a moderate risk of thunderstorms associated with a southwest change for North Otago and Canterbury during the afternoon and evening, and for the Kaikoura Coast and southwest Wairarapa in the evening and at night. These thunderstorms may bring localised heavy rain with intensities of 5 to 15 mm per hour and hail of 5 to 15 mm in diameter for Otago and Canterbury and 5 to 10 mm in diameter further north. Elsewhere, there is a minimal risk of severe convection or thunderstorms.

Issued at 7:40pm 18/09/2025

Valid from Midnight 18/09/2025 to Midday 19/09/2025

A strong southwest flow over the country eases during the day. There is a low risk of thunderstorms before dawn about the west coast of the North Island from Northland to Taranaki. For coastal Waikato, Waitomo, and northern Taranaki the risk of thunderstorms is moderate for a time early morning, with localised heavy rain with intensities of 5 to 15 mm per hour and small hail. There is also a low risk of thunderstorms about northeast Marlborough, Wellington, southern Kapiti and the east coast of the North Island south of Mahia Peninsula before dawn, and about the Gisborne coast after dawn. The risk of severe convection or thunderstorms about the rest of New Zealand is minimal.

Issued at 10:16am 18/09/2025

Valid from Midday 19/09/2025 to Midnight 19/09/2025

There is minimal risk of thunderstorms or significant convection during this period.