Sydneysiders have woken to thick fog this morning, with visibility reduced to 50 metres in some suburbs. Light winds this morning combined with high levels of moisture in the atmosphere, which was left over from yesterday's showers. The fog also kept the temperature a degree or two above average, reaching a low of 9 degrees in the city. The fog was thickest in Sydney's west and southwest. Visibility was as low as 50 metres in Richmond and Campelltown and 100 metres at Bankstown. The fog has also reduced visibility to 300 metres at Sydney Airport. This has prompted a road weather alert for all Sydney suburbs. The fog was not confined to Sydney, with both Newcastle and Canberra recording visibility as low as 100 metres. The fog should clear by about 9am this morning, although winds are expected to remain light, bringing the possibility that the fog could linger for a bit longer in the most prone suburbs.