At the risk of sounding like a swooning teenager feeling the first sharp pangs of young love, there's an especially intense sheen of blue in the skies above Sydney today. Why?

Basically, there are two reasons.

Firstly, strong westerly winds in the wake of a cold front which crossed the state yesterday have blown away any lingering air pollution.

Image: Hey, true blue. Source: Pixabay.

But while the westerlies have been blowing consistently at around 20-30 km/h for over 24 hours, they haven't really been strong enough to raise dust – not that there's much dust to raise in the eastern third of NSW after consistent and in some cases extremely heavy rainfall this year.

The second factor contributing to those deep azure skies over Sydney and much of the east coast is that the westerlies are exceptionally dry.

As late autumn and winter weather patterns set in over southeast Australia, westerly winds tend to blow on more days than not, and those winds tend to be bone dry east of the Great Dividing Range, once all the moisture has been squeezed out.

Indeed, Sydney's relative humidity at 2 pm on Wednesday was just 40%, a very low reading. And the less moisture in the air, the clearer it is.

And glorious on the Harbour pic.twitter.com/lBQNjPBw29

— Neale Ferguson (@nealeferguson) May 27, 2021

If you're lucky enough to be pretty much anywhere along the east coast this very sunny afternoon, good luck to you. But if you're in Sydney, be aware that the clear skies are not going to make it through to the weekend.

• Friday will be much cooler with tops of around just 18°C.
• Saturday will also be pretty chilly with tops of just 17°C and brisk southerly winds.

A large low pressure system forming in the Tasman Sea will be of more concern to Kiwis than Aussies.

If this thing had parked itself 1,000 km or so further west, we could have been looking at meteorological mayhem over the weekend.

Australia's east coast should well and truly avoid the worst of it, but hazardous surf and occasionally strong winds along parts of the NSW coast, including Sydney, will be a reminder of what's lurking offshore.