There is a heavy rain warning for the headwaters of the Otago lakes and rivers, with 120mm expected to fall in some areas between 9am and 9pm today.
A humid northerly flow precedes a trough, which would bring a "burst of heavy rain", the warning says.
MetService meteorologist Pete Little said the rain would be a "welcome" sight in most places.
He said the burst would be "short and sharp and then gone".
The heavy rain was expected to clear later tonight.
Areas within 15km of the main divide could expect 70mm to 100mm of rain, with 120mm likely close to the divide. At its heaviest 10mm to 15mm per hour were likely, with up to 20mm per hour closer to the divide.
