Southern and eastern areas of the South Island are to be hit with a cold front that could see expected highs halve in just 24 hours, MetService says.
The forecaster says a cold front will move up the country from the Southern Ocean, bringing dramatic temperature changes for some regions.
"Plenty of places in Otago and Canterbury will see a fall of 10 degrees from Tuesday to Wednesday," MetService meteorologist Alwyn Bakker said.
Alexandra is in for a particularly sudden drop, with a forecast high of 30C on Tuesday and just 15C on Wednesday.
"This isn’t the largest change in temperature they've ever recorded in 24 hours, but it is close," Bakker noted, "And if Alexandra doesn't rise above 15.7 degrees on Wednesday, they will see their coldest maximum temperature this summer."
Rain will also arrive, bringing some relief to parched areas of the South Island.
Bakker said some locations could see 40mm of rain in 24 hours.
"That's as much rainfall as parts of inland Otago have had all year."
Heavy rain watches have been issued for Otago, Southland, northern Fiordland, and the ranges of Westland south of Otira. Snow may even fall on the peaks of the ranges down to 1000m.
Cooler temperatures will continue as the front travels north but rainfall amounts are expected to decrease.
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