Dunedin and eastern parts of Otago are in for a drenching as a front moves in, ending a spell of sunny spring weather.

MetService on Tuesday morning issued a heavy rain watch for Dunedin, North Otago and Clutha, for 24 hours from 6pm on Wednesday.

The forecaster said a cold front was moving on to the southern South Island on Tuesday, with a strengthening northwesterly flow ahead of it, giving eastern areas a summer-like feel.

Christchurch was predicted to hit 27C on Tuesday.

The hot spell would be short-lived, however, with the front expected to bring rain and a significant drop in temperatures from Wednesday, MetService meteorologist Luis Fernandes said.

"We're going to see wetter weather settling in during Wednesday and Thursday, and then temperatures will take quite a bit of a dive heading into the last couple of days of the week," Fernandes said.

Friday's high for Christchurch is just 11°C, with frosty mornings possible over the weekend.

"It is very typical of this time of the year to see this sort of flip-flop between much warmer weather and then much cooler weather. Spring is a transition season, so we're going to continue seeing stronger fronts moving through from time to time," Fernandes said.

Further north, there is a heavy rain watch for the Westland and Grey District ranges, and the Canterbury High Country within 15km of the Main Divide; there is also an orange heavy rain warning for Buller, where surface flooding and slips are possible. 

— Allied Media

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