Bushfires this season have officially burnt the most land on modern record across eastern New South Wales.

In a special climate statement released on Wednesday, the Bureau of Meteorology said spring 2019 saw Australia's highest fire weather danger on record.

Even by the end of spring, the extent of the fires this season was exceptional; more than 1.65 million hectares had been burnt in New South Wales.

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On December 9, NSW Rural Fire Service Commissioner Shane Fitzsimmons tweeted that fires had burnt about 2.7 million hectares — an area greater than Wales.

Yes, Wales, the country.

Or if sport is more your thing, one hectare is approximately the size of a soccer pitch.

Between early September and the end of November, 220,000 hectares had been burnt in Queensland and still the fires rage on.

Fires have already occurred in every state and territory this season.

Normally, it would now only be the beginning of the fire season in the southern states, and traditionally the northern fire season would be winding down as summer rains arrived, but there is no indication that rain is coming any time soon.

Fire danger unprecedented

The fire danger wasn't just restricted to the east coast, with the rating for the country as a whole far and away the highest on record for spring since 1950.

Almost 60 per cent of the country had the highest accumulated FFDI on record, which go back to 1950. ( Supplied: Bureau of Meteorology )

"Spring 2019 saw the highest fire weather danger as measured by the Forest Fire Danger Index (FFDI), with record-high values observed in areas of all states and territories," the report stated.

The FFDI takes into account recent rainfall, a drought index, relative humidity, air temperature and wind speed to give a value that reflects how dangerous a fire is expected to be once it gets going.

It's what you see represented on the roadside fire danger signs: low, high, very high, extreme, catastrophic (code red in Victoria).

"More than 95 per cent of Australia by area had spring-accumulated FFDI values that were very much above average (highest 10 per cent of years), including almost 60 per cent of the country that was highest on record for spring," the report stated.

The accumulated FFDI for spring was far and away above pervious years. ( Supplied: Bureau of Meteorology )

Other big fire years for NSW

It is important to note there is a big difference in fires depending on where they are in New South Wales.

As a general rule, fires west of the Great Dividing Range are often more widespread, but because of lower fuel loads they burn with a lower intensity.

Fires on or east of the range, in more densely forested areas, burn with a greater intensity; when that intensity is combined with higher population density, there is greater risk.

According to the report, the closest season compared to 2019 was 1968, but even it was less extensive than this year.

Those fires also took place under severe drought conditions and were limited to the Hunter and Illawarra regions.

The 1968 season had a number of major fires, including one in the Blue Mountains that burnt for more than a month — the Australian Disaster Resilience Knowledge Hub attributes the Blue Mountains and Illawarra bushfire with burning through 1.5 million hectares.

Fires have already occurred in every state and territory this season. ( Supplied: Gena Dray )

Other major fires in eastern NSW include:

January 1994, when 800,000 hectares burnt around Sydney and the state's north-east

January 1994, when 800,000 hectares burnt around Sydney and the state's north-east Christmas 2001, when 750,000 hectares burnt on the southern fringes of Sydney and around the ACT, bringing significant smoke

Christmas 2001, when 750,000 hectares burnt on the southern fringes of Sydney and around the ACT, bringing significant smoke October 2013, most remembered for its rapid onset and significant loss of homes in the Blue Mountains

With the current heat event, South Australia is bracing for dangerous fire conditions until a cool change late Friday.

The worst of the fire danger is then expected to return to New South Wales on Saturday ahead of the change, with continued elevated fire danger in Queensland.

This week's update to the bushfire outlook didn't bring much in the way of good news.

Keep up to date with warnings from your local fire authority, ABC Radio and ABC Emergency on Facebook.