Rain, low cloud and thick fog have been descending on Australia's most populated areas, leading to significant travel problems on the main roads, rivers, harbours and at airports.
A large area of southeastern Australia, including Sydney, Melbourne, Canberra and Brisbane may all be impacted through to the Thursday morning peak hour.
Rain and low cloud have been enough to make travel challenging but the rain has also increased the moisture in the air, enabling thick fog to add to commuters woes.
As early as 5:30pm on Wednesday thick fog developed in western Sydney, slowing down drivers and contributing to accidents on the slippery roads. Visibility was reduced to less than 100 metres in some areas.
The fog should last through the night in western Sydney and may even develop close to the airport and city with potential to affect flights and ferry services.
Travel-delaying rain, low cloud and fog is also a significant risk in Melbourne, Canberra and Brisbane through to Thursday morning.
Skies should clear by about 8am in Sydney and Brisbane with help from freshening winds, whilst Melbourne and Canberra lurk in the grey, wet weather well into the day.
Looking further ahead showers are likely to persist on and off in Melbourne and Canberra on Friday before clearing in national capital in time for the weekend.
Sydney and Brisbane can look forward to mostly sunny but breezy days through to early next week with just the chance of brief showers in Sydney as the offending low pressure system slowly moves to New Zealand.
© Weatherzone 2013
12:38 EST Tropical Cyclone Jack has rapidly developed over the warm waters of the Indian Ocean in the past 24 hours, making it the 10th system to be named this season.