The message is clear as heavy rain pelts the lower South - be prepared.

A red-level heavy rain warning is in force for North Otago, Dunedin and coastal Clutha.

NIWA reports Dunedin has already had 75 percent of its normal monthly rainfall for October.

Otago Civil Defence group controller Matt Alley said they were continuing to monitor rain as it was falling.

"We have our emergency operation centre in Dunedin city and Clutha and a coordination centre in Dunedin as well, fully activated."

Residents and visitors to Central Otago's Omakau and Ophir are under a Boil Water Notice for the time being and drinking water tankers are at the Omakau Domain and Swindon Street.

Conserve water notices remain in place for Ranfurly, Naseby and Patearoa.

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