Low temperatures, light winds and the right amount of moisture in the air led to the formation of low cloud and fog, reducing visibility across large areas of NSW, particularly the Riverina district on Sunday.

Narrandera airport, in the Riverina, had visibility reduced to only 450 metres even as late as 12:30pm. Griffith airport also had visibility reduced to 300 metres as late as 11am and Albury had visibility down to only 100 metres at 9am.

The main ways to determine visibility are through direct observations by weather observers or by using instruments called ceilometers and visibility sensors. These instruments work by basically sending out a light source and measuring how much of that light is returned to the instrument. They are most commonly used at airports to provide valuable information to pilots for landing and take-off. However, forecasts and observations for low visibility are important along roadways, railways and shipping routes.

The fog and extensive low cloud led to a cold and gloomy day, temperatures still only about 7 degrees at both Yanco and Narrandera at 2pm, 8 degrees below the June average maximum. In the sunshine down the road it was about 5 degrees warmer. Prior to today, the coldest June day in the past 20 years was a 7.8-degree maximum at Yanco and 8.2-degree maximum at Narrandera.

Visible satellite image showing low cloud and temperatures in the Riverina and surrounds at 2pm on Sunday

Fog is a chance on Monday morning again for large areas east of the Great Dividing Range. There is also the chance of frost along the ranges as temperatures will be cold.