The city is shivering through its coldest week since early July, including a rapid 10-degree drop in temperatures on Sunday that caught many people on the hop.

The good news is Monday's top of 16.3 degrees may be the lowest maximum for a while. And, after a few days barely reaching the high teens, the coming weekend is likely to much milder including 27 degrees forecast for Sunday.

But a cold front expected to arrive early next week may punish those who prematurely pack away the winter clothes.

"It'll be spring-like ahead of the front but July-like behind it," Brett Dutschke, senior meteorologist at Weatherzone, said.

The most recent front was not particularly strong but it dragged "polar-type air a long way north", he said.

Snow was reported in the Blue Mountains on Sunday and even Dural to Sydney's north-west.

In Victoria, the mercury at Mt Hotham dropped to as low as -10.4 degrees, the state's coldest reading since August 1974, according to the Bureau of Meteorology. It was also Victoria's first sub-10 reading since 1986.

"We're unlikely to see an air mass as cold" until next winter, Mr Dutschke said.

As a consolation, Sydney has been averaging just under nine hours of sunshine this August.

At this point, it's the sunniest August for the city in 22 years but that ranking will probably drop over the final few days of the month, he said.

The sunny conditions, though, are a pointer to the ongoing dry spell for the city.

If, as forecast, Sydney collects only a couple of millimetres of rain at most over the next few days, the city will post its driest July-August stretch since 1995, Mr Dutschke said.

Sydney has had about 37 millimetres of rain for the two months, about one-fifth of the long-run average.

Weatherzone is owned by Fairfax Media, publisher of this website.