A severe thunderstorm warning is in place for Porirua and surrounding areas, with forecasters warning of intense downpours and hazardous conditions through midday Sunday.
MetService issued the alert at 11:52am, covering Porirua City, Hutt City, Upper Hutt City, Wellington City and South Wairarapa.
Weather radar detected severe thunderstorms near Wellington, Lower Hutt and Porirua about 11:45am. The system is moving east-southeast and is expected to track across Wellington and Wainuiomata by 12:15pm, reaching Lower Hutt, Upper Hutt and the southern Remutaka Range by 12:45pm.
Forecasters say the storms are likely to bring very heavy rain, raising the risk of surface and flash flooding in streams, gullies and urban areas. Driving conditions may become extremely hazardous.
An update is due at 12:45pm.
Looking ahead, a heavy rain watch has been issued for parts of the wider Wellington region not covered by the thunderstorm warning, including Kāpiti Coast and Horowhenua. The watch runs for 31 hours from 11am Monday to 6pm Tuesday.
MetService says periods of heavy rain and possible thunderstorms could approach warning levels, with a moderate chance the watch will be upgraded.
A strong wind watch is also in place for Wellington, including Porirua, from 4pm Monday to 9am Tuesday. Southerly winds may approach severe gale in exposed areas, with a moderate chance of escalation to a warning.
Residents are advised to stay alert, clear drains where safe, and avoid flooded areas. Motorists are urged to drive to the conditions and allow extra travel time.