Heavy showers and isolated thunderstorms sweeping over West Auckland were expected to ease later this evening.
The large thunderstorms formed over the Waitakere Ranges and Manukau Heads area, WeatherWatch said.
The forecaster warned that the localised downpours could be heavy and may lead to rapidly rising streams.
Flash and surface flooding was also possible, WeatherWatch warned.
The heavy showers may spread further east this evening, developing stretches of heavy showers along the entire western Auckland coastline.
MetService duty forecaster Heath Gullery said there was a chance the heavy showers and isolated thunderstorms could drift onto Auckland city.
The high winds and showers were expected to ease later this afternoon, he said.
"They formed along the west coast of Auckland near Hokianga Harbour."
Due to the slow-moving nature of the thunderstorms, there was potential for some minor surface flooding, Mr Gullery said.
An isolated funnel cloud or small tornado may also be possible, WeatherWatch warned.
Mr Gullery said that with any kind of thunderstorm system, there was a chance of a small tornado or a funnel cloud.
"But those things are pretty small-scale, so we couldn't predict where or when."
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