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Southerners will be looking to dust off their fans and sprinklers this week.
Christchurch is looking to reach 29degC today followed by a scorching high of 36degC on Tuesday as a ridge of warm weather moves across the country.
MetService meteorologist Alwyn Bakker said this is 13degC above the city's average temperature for this time of year.
"Christchurch is currently looking at 3 days in a row with more than 5degC above average."
It is considered a heatwave when temperatures are consistently 5degC above average for five days.
It is a similar story further south with Timaru expecting to reach 28degC on Monday and 34degC on Tuesday.
Dunedin and Nelson are also in for some warmer days this week, reaching 30degC and 26degC on Tuesday respectively.
The sunshine is not expected to last all week with a front expected to bring a cool change to much of the country from about Thursday.
It follows a bleak summer so far in Christchurch and Dunedin.
"People would have felt these long stretches of below-average temperatures over the Christmas period," a MetService meteorologist said.
The south was battered by thunderstorms, heavy rain and strong gales last week.