MetService is defending the lack of warning in Wellington, before it was battered by torrential rain and flash flooding early today.

Karori man Philip Sutton hasn't been found since his home flooded.

Wairarapa and Wellington - excluding Porirua - now sit under a rare red warning until late tomorrow.

A State of Emergency's been declared, with warnings to evacuate from low-lying areas.

MetService's Heather Keats says limited warning's possible for localised thunderstorms - because they develop so quickly.

"You could be 40 kilometres up the road and have no rainfall recorded at all, and then you could be underneath it and then receive 80 millimetres in an hour." 

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