Monday's record temperatures in Otago were a one-off, at least for coastal areas for the next few days, the MetService says.
Dunedin sweltered with a high of 34.6degC on Monday while other main centres in the region also hit the 30degC mark.
It was back to reality yesterday, with Dunedin recording a high of just 16degC.
It was sunny, but the familiar southwesterly meant many people kept their coats on.
Wanaka was the only main centre to officially reach 20degC.
MetService duty meteorologist Claire Flynn said a cold front was to blame and a ridge sitting to the west would not feature extreme temperatures.
"The air mass itself is just not as warm,'' she said.
"[The temperature] won't get to quite those extremes [of Monday].''
Those of us worried about Christmas Day weather should take a deep breath and relax, as all main centres seem set to be fine.
The Christmas Day temperature is forecast to reach 20degC in Dunedin and Oamaru, with holiday spots Alexandra (24degC) and Wanaka (25degC) the places to be.
Queenstown would reach 21degC and Balclutha 18degC.
Ms Flynn said the approaching ridge would mean more settled weather.
There would be some cloud around on Christmas Day over coastal areas but it would be otherwise fine, she said.
"There will be a stretch of fine days over the Christmas period. Temperatures might be a bit warmer on Boxing Day but that would be more likely inland.''
There could be some isolated showers on Sunday but most would not see them, Ms Flynn said.
National Institute of Water and Atmospheric Research principal scientist Chris Brandolino said a "happy high'' was set to lie just west of New Zealand, bringing sun and warm temperatures to large parts of the South Island tomorrow and Christmas Day.
"[The] high is expected to pass through over the weekend, bringing plenty of opportunity to enjoy the outdoors this Christmas.''
