Flights into and out of Dubbo were delayed on Friday morning because of a thick fog that blanketed the city.
The fog started to set in from 6pm on Thursday and deepened overnight, senior forecaster at the Bureau of Meteorology Jordan Notara told the Daily Liberal.
"A rain band went through yesterday and created additional moisture in the Dubbo area and that caused conditions to be favourable to fog," he said.
"The fog covered a broad area, not just in Dubbo but other parts of the central west too.
"The depth of the fog was quite significant and that caused the fog to have difficulty clearing."
Mr Notara said it was normal for Dubbo to have a higher proportion of its fogs between June and August.
Dubbo received 4.2 mm of rainfall to 9am this morning, Mr Notara said.
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Western Region Traffic Tactician Inspector Ben McFarlane said while people generally drive to conditions when there is fog, some may people not.
He urged motorists to slow down when there is heavy fog.
"Avoid the use of high beam because that reflects back off the fog," he advised.
"If the fog is that thick then avoid the trip."
Inspector McFarlane said in foggy conditions it's acceptable for motorists to activate their hazard warning lights when their vehicle is moving or not.
"It's also an opportunity to activate your fog lamp.
"Avoid dazzling other drivers and don't make it harder for oncoming vehicles."
Animals also "creep closer to the road and present more danger when there is heavy fog", Inspector McFarlane said.