A large band of raised dust has travelled across NSW during the last 24 hours, browning skies and reducing air quality.

Gusty northwesterly winds ahead of an unseasonably strong cold front caused dry topsoil to become airborne in western and southern NSW on Tuesday afternoon. This raised dust split into two bands as it spread over NSW and southern Queensland during Tuesday night.

By Wednesday morning, satellite imagery showed that the longest band of dust stretched from Sydney to Birdsville, spanning a distance of nearly 1,500 kilometres.

Image: Two bands of raised dust can be seen sweeping over eastern Australia and the Tasman Sea on Wednesday, February 13th.

Large dust storms like these can see topsoil lifted a few kilometres into the atmosphere and transported across states and oceans. A dust storm during November last year caused a large cloud of dirt to drift across the Tasman Sea towards New Zealand. It appears that this week's dust will also make it some way over the Tasman before completely dissipating.

Air quality index values reached Hazardous in the Illawarra and Very Poor in Sydney during Tuesday night and early Wednesday morning. These are the two highest categories in a six tier scale.

While skies were still visibly reddened in Sydney on Wednesday, this dust was suspended high above the ground. The city's air quality actually improved across most of Sydney from early on Wednesday morning.

This week's dust storm, and the several others that preceded it in recent months, is a manifestation of the drought gripping Australia's southeast inland. Last year was the Murray Darling Basin's seventh driest in 119 years of records.