Thousands Of Firefighters Continue To Battle NSW Bushfires As Air Quality Concerns Grow

Temperatures dropped across NSW on Tuesday night with a southerly bringing welcome relief from choking smoke but firefighters are concerned the change could cause more problems.

There were 83 bush and grass fires still burning across the state.

Of those, 40 blazes were still out of control, including a dozen at watch and act level.

An emergency warning issued for the Little L Complex, Yengo National Park fire in the Singleton area on Tuesday afternoon was downgraded to a watch and act level just after 9pm.

An emergency warning issued for the Three Mile blaze in the Hawkesbury region, on Sydney's northwest fringe, was also downgraded to a watch and act level just before 4pm.

The fire is east of the so-called mega-fire centred around Gospers Mountain which was also at watch and act along with two neighbouring blazes.

Temperatures reached 42.4C in Richmond on Tuesday afternoon before dropping to 28C there before 4pm as cooling winds arrived.

"This change has helped to ease some of the very smoky conditions but the smoke still continues to be reasonably heavy," a bureau forecaster told AAP.

Catch up on Tuesday's bushfire coverage below.