Strong winds hit across the weekend - gale force at time - making official temperatures look deceiving for the Illawarra, South Coast and Southern Highlands according to the Bureau of Meteorolgy.
The strong winds will, however, ease on Monday as a high pressure system moves in and thaws the coast.
"Over the weekend we did get some days where we had very, very strong winds, even overnight Albion Park managed wind gusts of 80km/h about 2am and I think the night before was quite similar," the Bureau's Helen Kirkup said.
"Yesterday through the day it got to a top of about 18 degrees for Albion Park but probably only felt 14 at most."
Ms Kirkup said the cold air mass moved over NSW across the weekend with the "air trajectory coming from Southern Ocean", bringing chilling overnight temperatures and a sprinkling of snow to the Snowy Mountains region.
"Sunday morning particularly ... we had some close to May records in terms of night time temperatures - we were down to -1 in Moss Vale," she said.
"Along Wollongong down to Jervis Bay we were down to about 9 or 10 along the coastline, Nowra was down to 5 which was 4 below average, even Wollongong [overnight low] at 10 is three below average."
Perisher and Thredbo resorts received a dusting of snow on Saturday before clearning on Sunday, though Ms Kirkup said overnight temperatures were below zero which were great for snow-making machines.
Just before 8am on Monday temperatures for Sydney, Melbourne and Brisbane were hovering around 10 to 11 degrees, while at Albion Park it was 12 degrees.
It was brisk for other capitals around the nation also at 8am - seven degrees in Hobart, six in Canberra and 14 degrees in Adelaide.
Both Albion Park and Wollongong were expecting a top 19, mostly sunny with some clouds for the start of the week.
Ms Kirkup said the actual forecast would look similar to the past few days but the difference was in the winds, with this week feeling more like what it reads on a temperature gauge.
"The actual daytime temperatures will be similar but it's absolutely going to feel a bit warmer than it has been with that ridiculous westerly that's been coming through," the meteorologist said.
"This high pressure system becomes established over the top of us, so it's just going to be light winds mostly for Tuesday and Wednesday."
The meteorologist said there would be a southerly wind change on the coast later in the week, while it would remain "reasonably dry" for the region. The cool nights are expected to remain until at least the middle of the week