Greg Mullins, who was Fire and Rescue NSW commissioner from 2003 to 2017, says Sydney will likely experience devastation greater than 1994, when hundreds of suburban homes were lost. "The worst is to come because it's going to get hotter and drier and there's no significant rain in the outlooks," Mr Mullins said. Loading Replay Replay video Play video Play video "We've got massive fires that are too big to put out without rain. They are going to get bigger and they are going to come into Sydney suburbs, the South Coast, the Central Coast." Mr Mullins said the number of homes lost this season was more than three times the previous record, with destruction this year so far confined to regional areas.

"Formerly all of our big losses have been places like the Blue Mountains, Sutherland, Warringah and Lane Cove," he warned. "The fires haven't even reached Sydney suburbs yet. People need to brace themselves. Former NSW Fire and Rescue Commissioner Greg Mullins (centre). Credit:AAP "They are going to see unprecedented losses, unprecedented fire, health issues with smoke, heatwaves and the science is in - this is all underpinned by a warming climate." Some 225 homes and other buildings were destroyed in the summer of 1993-94, when four people were killed. The most significant losses were in the Sydney region.

Loading Firefighters have expressed concerns about the impact the southerly change could have on Wednesday on fire grounds surrounding Sydney. Temperatures soared in NSW on Tuesday, with hazardous bushfire smoke pollution blanketing much of the state. More than two million hectares of land has been burned to date this season and there are almost 90 fires burning across NSW, with 40 uncontained, including a so-called megafire northwest of Sydney. The Bureau of Meteorology says although conditions have eased, the smoke will continue to linger on Wednesday and the next few days.

Smoke across the Sydney basin was so thick at one point on Tuesday it was deemed 11 times poorer than typically "hazardous" levels. Meanwhile, Corrective Services NSW staff evacuated inmates from Oberon Correctional Centre in the Central Tablelands region on Tuesday night due to nearby bushfires threatening the centre. Officers transported the 121 minimum-security inmates to Bathurst and Lithgow correctional centres. Air quality was on Wednesday morning deemed "hazardous" across Sydney's east, southwest and northwest, despite improved visibility. "We are expecting [the smoke] to continue over the next few days ... with fires to the southwest and north of Sydney, we need easterly winds to help ease the smoke," a BOM forecaster said.

Total fire bans are in place on Wednesday for northwestern NSW, the northern slopes and the central ranges. Fire danger is severe in the northwestern region and "very high" in the north of the state as well as the upper central west plains, the central ranges, the southern ranges, the southern slopes and the ACT. On Tuesday evening, an emergency alert was issued for the 67,000-hectare Little L Complex fire near Wollombi in the Hunter region. Residents living in the Glenroy Estate area were told to seek shelter from the fire as it was too late to leave. However, the blaze has since been downgraded.

An emergency warning had also been issued for the Three Mile blaze in the Hawkesbury region, but it was downgraded before 4pm. "The fires just around Sydney alone - there is kilometres and kilometres of back-burning to do to try to lock the fires in," Mr Rogers told ABC TV. Loading "We've got a lot of people that are very determined to get these fires under control as quickly as we possibly can." Prime Minister Scott Morrison on Tuesday encouraged Australians to heed expert advice on bushfire warnings and air pollution.

"I can reassure everyone the nationally-co-ordinated effort and the specific state efforts leading the response in each of their jurisdictions has been incredibly professionally deployed," Mr Morrison told reporters. Some 2700 firefighters were in the field on Tuesday, supported by water-bombing aircraft. Former fire chief Mr Mullins said he was worried how volunteers will cope when the weather heats up even more in January and February. "Everyone is getting pretty worn out and, in my experience, that's where all the bad stuff happens," he said. "The sheer scale of these fires - we haven't had this before. We haven't had these losses, we haven't had them at this time of year, they haven't been this big. We're really up against it."