A dust storm sweeping across NSW hit the Blue Mountains on Thursday morning, heading towards Sydney.
The NSW Rural Fire Service posted a photo of the storm over the Blue Mountains at 8.35am.
Parts of outback NSW, including White Cliffs, were cloaked in dirt on Tuesday.
Forecasters are closely monitoring a system headed towards the state and associated high winds that could pick up masses of loose dust caused by drought conditions.
"If it does happen it could have big impact," Bureau of Meteorology forecaster Anita Pyne said.
"Dust storms can effect transport and even stop planes from landing."
A cold front that moved through South Australia on Tuesday, with a low pressure trough over NSW, is responsible for current conditions.
“That low pressure system will bring strong westerly winds to NSW,” Ms Pyne said.
“These strong winds have the potential to pick up dust and raise it high into the atmosphere.”
Winds could hit 45km/h on Thursday and Friday.
“We can't rule out any events before then, but its more likely later on Thursday and into Friday,” Ms Pyne said.
People with asthma, diabetes or a breathing related conditions are advised to be cautious.
Health warning as dust storm looms
NSW Health is urging people to be aware of the health risks of dust storms as a large dust storm is forecast to move across NSW, potentially affecting Sydney.
Air quality in the Sydney basin could be poor for Thursday and possibly extending into Friday.
Director of Environmental Health Dr Richard Broome said it was especially important for children, older persons, and people with chronic respiratory and cardiovascular conditions such as asthma, chronic bronchitis, emphysema and heart disease to limit their time outside and not engage in vigorous exercise during a dust storm.
“If possible, stay in air-conditioned premises where filtration systems can help to reduce dust particles in the air,” Dr Broome said.
“Dust may aggravate existing heart and lung conditions and cause symptoms like eye irritation and cough.
“Symptoms can occur for several days after dust is inhaled, so people with the chronic conditions need to be vigilant with their treatment programs.
Dr Broome said if symptoms do not settle, seek medical advice immediately.
“If you are on home oxygen treatment, continue as prescribed and if breathlessness worsens, contact your doctor,” he said.
“Healthy adults may also feel the effects of fine particles that can irritate the lungs, so it’s wise to reschedule or cut back on prolonged or strenuous outdoor activities when dust levels are high.
“These particles can cause a variety of health problems, such as itchy or burning eyes, throat irritation, runny nose and illnesses such as bronchitis.
In case of emergency always remember to dial triple zero.
AAP, with Madeline Crittenden