At Observatory Hill, near the CBD, maximum temperatures were 2 degrees above average for the January-June period, second only to 2016, according to the Bureau of Meteorology.

Statewide, daytime temperatures have been 2.38 degrees above the norm, half a degree warmer than the previous record set a year earlier. Rainfall has averaged 148.1 millimetres for the state, or half the norm, and the driest start to a year since 1986.

The dry, warm spell has extended into July. Sydney on Monday notched its sixth day this month of 20 degrees or warmer weather, with up to six more expected before Sunday.

Only 2013 has posted 12 such days in July, Lynette Bettio, a bureau climatologist said.

Fire authorities are also in discussions to determine which areas of the state that normally start their official fire seasons on October 1 will have their restriction moved to September 1.

Loading

An indication of increased fire activity is that crews dealt with 525 bush and grass fires in the past week, almost twice the 276 reported for the same period a year ago, Matt Sun, an RFS spokesman, said.

In the past fortnight, the RFS responded to 142 reported escaped or illegal landowner burns across the state, the agency said on Friday.

"You can't just light them and walk away", Mr Sun said, adding that with the dry conditions and winds, it's "quite easy to lose control" of blazes.

The Bushfire & Natural Hazards CRC is due to release its southern Australia bushfire outlook on September 5, with many areas expected to face a more active than usual summer.

The research body, which released its northern Australian seasonal outlook last week, declined to comment to Fairfax Media on the prospects for NSW.

Scientists say a climate shift towards drier winters has been evident for several decades across much of Australia, including the south-west and the south-east. Among other effects, fire authorities have narrower windows to conduct hazard reduction burns that can cut the risk of bushfires near population centres.

Troy Grant, Minister for Emergency Services,  said despite cold temperatures across the state, now was the time for residents and land managers to prepare for bushfires.

“We saw with the Holsworthy fire in April, as well as a Watch and Act fire west of Port Macquarie just last week, that bushfires can strike out of season and it is vitally important to be prepared,” Mr Grant said.

“This means doing really simple things like cleaning your gutters, removing combustibles from your yard, ensuring hoses can reach all corners of your property and completing or updating your bushfire survival plan, so you and your family know what you will do in the event of a bushfire."