Why is eastern Australia so cold?

It's chilly in the east but fine for most of the rest of Australia - and a glance at the synoptic chart explains why this is happening.

A very strong and slow-moving high-pressure system is sitting in the Great Australian Bight at the moment and that's dominating Australia's weather pattern.

The air around a high-pressure system spins anticlockwise and the isobars - the lines on the map - show the general direction the wind is blowing.

In the east, the wind is being drawn from sub-Antarctic regions of the Southern Ocean and is blowing from the southwest, directing cold air across Tasmania, Victoria, NSW and even Queensland.

That flow, which comes in the wake of a series of cold fronts now east of Australia, has kept the southeast chilled for days, with snow falling as low down as 500 metres in Victoria and 300 metres in Tasmania on Wednesday.

This morning, Adelaide had its lowest minimum for the year: 4.8C.

The effects are now being felt further north.

Sydney had its coldest morning for the year and the coldest May morning since 2011, with a low of 7.9C, but the wind dropped the apparent temperature by a further 4C or so.

Temperatures in Sydney's suburbs were even lower, with many hovering around the 4C mark and Canterbury registering just 1.5C.

Canberra recorded a low of minus 4.7C.

Temperatures in the Blue Mountains got down to minus 2C and there is widespread frost up and down the NSW Tablelands.

It was only 3C in the Queensland city of Toowoomba on Thursday morning, but the apparent temperature was minus 3C because of wind chill.

A high-pressure system generally means sunny, settled weather, so most of Australia will be dry and clear.

The high is moving slowly east and will be over southwestern Victoria by Friday.

It should bring sunshine to the southeast at least until Monday, although in some areas mornings may be frosty.