Otago's bracing for severe flooding, from torrential downpours

A Red Heavy Rain Warning's in force for North Otago, Dunedin and coastal Clutha.

Flood response crews have opened coastal river mouths in the region - and Emergency Management Minister Mark Mitchell is heading to Dunedin.

MetService warns some areas could get about two months' worth of rain - by the end of Friday.

Clutha Mayor Bryan Cadogan says local catchments are the biggest flooding risk.

He says the Tokomairiro, Pomahaka and the Clutha all are potentially dangerous.

Orange Warnings still apply to parts of Bay of Plenty and Tairawhiti.