The Bureau of Meteorology has issued a warning for gale force winds along much of the NSW coast for Wednesday and Thursday. A separate alert for cold temperatures has been issued for southern inland regions.

"Large and powerful surf conditions" are expected from Wednesday evening. These will make surfing, swimming and rock fishing hazardous until Friday, the bureau said.

"The wind chill will also be significant," Jacob Cronje, senior meteorologist at Weatherzone, said. "The evenings are going to feel very, very cold."

The winds are likely to increase in strength from Wednesday afternoon as the front moves through and will only start to slacken by Friday, he said.

That means the forecast overnight lows of 10-11 degrees from now until Saturday will probably feel a couple of degrees colder, particularly in the central business district and coastal strip, Mr Cronje said.

The bureau is forecasting daytime temperatures to reach 22 degrees on Wednesday before retreating to 19 degrees on Thursday. They will then recover to 23 degrees - or roughly the April average - by Saturday.

Maximum temperatures have been above average for the past two weeks and are running more than a degree above the long-term norm for April. That trend will extend the unbroken run of warmer than usual months well into a fifth year, according to bureau data.

Cold snap

That track record, though, may be of little consolation to many Sydneysiders and those across the country's south-east as the burst of wintry weather moves in.

Inland locations such as Canberra and Armidale should cop "the first proper frost of the year", Mr Cronje said.

The shift towards cooler conditions, though, has also been accompanied some welcome rains, particularly in the grain-growing regions of southern NSW and Victoria. That's made for a timely "autumn break" as farmers sow winter crops.

"Inland parts have received healthy totals of rainfall," Mr Cronje said.

(See bureau chart below of rainfall totals over the past week.)