Oh to be in Sydney now summer’s there

While Aucklanders are soaking in hot tubs and putting on their winter coats, Sydneysiders are turning up the air conditioning, or donning their togs and heading for the beach.

On this side of the Tasman we may be recovering from a blast of cold temperatures, but Sydney residents are being told to stay inside to avoid the scorching heat.

The good news is that some of that warm weather is headed this way.

"It's just a cold outbreak," said Bob McDavitt, the MetService weather ambassador. "It will be gone by this weekend."

As if on cue, the weather had warmed a bit to 19C by midday yesterday.

By comparison the Sydney Ambulance Service yesterday urged people to avoid the sun as the city sweltered. By midday, temperatures were pushing 37C and went over 40C by the middle of the afternoon..

Firefighters were on high alert, power use soared as air conditioners were turned on and commuters were warned that trains might have to slow down in the heat. Parents were told they may have to collect their children from school early.

In Auckland, it has been unseasonably cool since last week.

After hitting 23C in mid-November, the high in the city on Saturday was only 15C.

"[That's] a maximum temperature you would associate with late winter rather than late spring," said Jim Salinger, a principal climate scientist at the National Institute of Water and Atmospheric Research.

The difference between temperatures in Auckland and Sydney stemmed from the wind direction and slightly below-average sea temperatures, Dr Salinger said.

"The air that's arriving at Auckland is originating somewhere west of Tasmania," he said, "whereas for Sydney at the moment, they've got hot northwesterlies flying out of central Australia.

"Should the airflow [to Auckland] change and start originating off eastern Australia, things will warm up," he said.

That's what meteorologists are projecting for the weekend: fine and sunny weather with highs of 20C to 22C.