Sydney CBD in the middle of winter generic cold snap.

Sydney is headed for its first cold snap of the year. Photo: Michele Mossop

A wintry blast is heading Sydney’s way that will knock temperatures 14 degrees below where they were last week, Weatherzone said.

The city’s balmy April will be a fading memory as maximums will reach just 16 degrees on Saturday and 17 on Sunday, the Bureau of Meteorology said.

‘‘The wind chill on those days will definitely drop those temperatures by 3 degrees or more,’’ said Guy Dixon, a meteorologist at Weatherzone, noting the bureau’s forecast for winds of 25-35 km/h on Saturday and 25-40 km/h on Sunday. The weekend should see the coolest pair of days since last August, he said.

A rain sodden gloom shrouds the Sydney skyline as winter approaches.

Winter is approaching. Photo: Dallas Kilponen

Weatherzone's senior meteorologist Brett Dutschke said the cold blast is likely to be the strongest this early in the season for five or six years.

"Some places (in southern Australia) may even be colder than any winter day in the past two years and possibly colder than any day this early in the season in more than 20 years," Mr Dutschke said.

"Temperatures will drop as much as 10 degrees below the early May average and be as much as 25 degrees colder than what it was a month ago," he said.

Tropical rains brought an unusual autumn break for farmers.

Tropical rains brought an unusual autumn break for farmers. Photo: BoM

The pool of cold air will cover a wide region. "This Friday and Saturday will feel like the coldest of winter days in South Australia, Victoria, the ACT, New South Wales and southern Queensland," Mr Dutschke said.

"Temperatures will struggle to reach the mid-teens due to cloud and frequent showers. The wind will make it feel colder than 10 degrees at times."

If Goulburn to Sydney’s southwest fails to exceed the forecast eight degrees on Saturday it will be its coldest day since winter 2011 and coldest day this early in the season in at least 20 years, Mr Dutschke said.

Past 12 months still quite dry for west and east.

Past 12 months still quite dry for west and east. Photo: BoM

Mild April

The cooler conditions will end a lengthy period of generally warmer-than-average conditions for Sydney.

As recently as April 24, the city enjoyed a maximum just a shade under 30 degrees, and the warmest so late in the season since 1953, the bureau said

In fact, Sydneysiders have had little use for cold-weather clothing so far this autumn, with just one day in April when the mercury failed to reach 20 degrees, and no nights below 12 degrees.

While last month was a cloudy one for Sydney – with 90 minutes less daily sunshine making it the gloomiest April since 1990 – it was another warm one.

“It was a month of mild days and mild nights,” said Agata Imielska, senior climatologist with the bureau. “There’s not been a lot of jacket-wearing weather.”

Last month’s weather highlights included 12 days of 25 degrees or warmer days, compared with a long-term average of five. The 29.9 degrees posted on April 24 was also the warmest day so late in the season since 1953. April would typically have six days with maximums below 20 but last month only had the one.

Maximum temperatures were 1.4 degrees above average and minimums 1.2 degrees higher. Earlier in the month, the city ended 36 days of at least 22 degrees – the third longest on record –  while last Sunday’s rainy chill snapped 160 days of 20 degrees or warmer, the seventh longest such stretch.

This weekend’s cool spell may be followed by another drop in temperatures from next Wednesday when a further cold front comes through, Weatherzone’s Mr Dixon said.

Rainy days

During April, rain fell on roughly every second day in Sydney, curbing average daily sunshine to 5.4 hours, although totals for the city ended marginally below the long-run average at just over 121 millimetres.

Statewide rainfall was also just below the average for the month. Temperatures were also on the warm side, with almost all of NSW reporting average minimums in the top 20 per cent over the past century for April, Ms Imielska said.

Nationwide, large parts of inland Australia reported record rainfall, some of which also found its way to south-eastern regions to give farmers in Victoria and parts of NSW their best autumn drop for years. The moisture came largely from tropical systems, however, rather than more typical winter-like storms.

“It was not your classic autumn break,” Ms Imielska said.

Queensland posted its warmest minimums on record while two-thirds of Victoria recorded overnight temperatures in the top 10 per cent of years.

Last year was Australia’s warmest on record and meteorologists say 2014 is shaping up to be another unusually warm one not least because of the growing likelihood of an El Nino weather pattern forming in the tropical Pacific.

Past El Nino years have been set global temperature records and have typically brought hot, dry conditions to much of Australia as changing wind patterns tend to shift rainfall away from the continent.

A background warming caused by climate change is also increasing the likelihood that heat records will be broken, scientists say.

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