Swathes of New South Wales awoke to temperatures well below what would normally be experienced in December. 

From the Northern Rivers to the Australian Alps, overnight temperatures dipped up to three to six degrees below the December average. In the north, Coonabarabran dipped to 10 degrees, six below average. Byron Bay's overnight low of 16.1 degrees was close to four below average and was the lowest December minimum in eight years.  

Further south, Goulburn's minimum was 4.8 degrees and Braidwood's 4.3 degrees; 5.9 and 6.3 below average respectively. The western suburbs of Sydney also experienced the chill. Richmond's low of 10.1 was 6.2 degrees below average and the coolest December night in six years. Elsewhere in the Sydney Basin, Penrith dropped to 12.7 degrees and Campbelltown 10.2. 

A deep low pressure system over the Tasman Sea continued to move away from the mainland overnight. This allowed skies to begin to clear and winds to ease over eastern parts of the state, as a high became established in its wake. This high, which was already established over central and western parts of the state, along with the low moving away, allowed for mostly clear skies and light winds overnight. The perfect ingredients for cool overnight temperatures. 

Image: Clear skies over much of New South Wales early Sunday morning. Source: Himawari-8 satellite

Another below average morning is expected on Monday as the high brings a similar set of conditions on Sunday evening and into early Monday morning.