MetService is advising Dunedin residents to clear their drains and gutters in preparation for heavy rain and surface flooding.
The weather forecast for the 33 hours starting at 3am on Thursday through to noon on Friday in North Otago, Dunedin and Clutha is for periods of heavy rain, in amounts which "may approach or even exceed" warning criteria.
While an official warning has not yet been issued by MetService, the forecaster said the chances of one being released sometime today were "high".
A brief period of heavy rain was expected this afternoon and evening, before easterly rain set in on Thursday morning.
Niwa data showed normal rainfall in Dunedin could reach 60mm in the month of October, but the rainfall totals over the next three days could exceed that.
MetService said streams and rivers might rise rapidly, and surface flooding, slips and difficult driving conditions were possible.
"Clear your drains and gutters to prepare for heavy rain. Avoid low-lying areas and drive cautiously."
Emergency Management Otago stakeholder engagement adviser Erica Andrews said the organisation would continue to keep a close eye on the situation, and advised residents to keep up to date with the latest forecasts and check their website for information.
In Southland, the Milford Road (State Highway 94) is closed from East Gate (Hollyford) to Donne River (Westgate) as rain has increased the chance of avalanche and snow is forecast, Milford Road Alliance said.
Heavy rain was expected to ease to snow showers today and snow showers will turn to rain on Thursday.
"It is possible the road will be closed overnight on Wednesday."
