A hazard reduction burn is causing large amounts of smoke across the Southern Highlands.
The 3700 hectare burn is taking place in the Catchment Area to the east of the Hume Highway and generally in a North East direction from Mittagong.
Rural Fire Service crews want to take advantage of the favourable weather conditions.
With the cooler overnight conditions it's highly likely that an inversion layer will hold the smoke at low levels, so drivers need to take care.
Inspector Ben Shepherd from the NSW Rural Fire Service says people with breathing difficulties should stay indoors.
IMAGE CREDIT: RFS Southern Highlands Team