"We have never seen this many fires concurrently at emergency warning level," New South Wales Rural Fire Service Commissioner Shane Fitzsimmons told public broadcaster ABC. "We are in uncharted territory." Bushfires are common in Australia and firefighters had already been tackling sporadic blazes for months in the lead up to the southern hemisphere summer.
But this is a dramatic start to what scientists predict will be a tough fire season ahead - with climate change and unfavourable weather cycles helping created a tinderbox of strong winds, low humidity and high temperatures.
So far there have been no reports of fatalities, although there were reports of buildings set alight and people trapped in their homes.
The fact the blazes were spread along a roughly 1,000-kilometre (620-mile) stretch of the seaboard left emergency services struggling to cope, even with the help of around 70 aircraft.
"Today has been a difficult and dangerous day. Unfortunately, many people have called for help but due to the size and speed of the fires we couldn't get to everyone, even by road or helicopter," New South Wales firefighters said.
Authorities in the state said fires had breached containment lines and forced the closure of the Pacific Highway linking Sydney and Brisbane in two places, although one area has since reopened.
On Queensland's Sunshine Coast, police ordered the total evacuation of Tewantin, a suburb of 4,565 people, before scaling back the order.
In some areas, residents were stuck and told to simply "seek shelter as it is too late to leave". Local radio stopped normal programming and provided instructions about how to try to survive fires if trapped at home or in a vehicle.
Across the central coast, residents took to social media to post photos and videos of smoke-laden tangerine skies and flames engulfing storeys-tall eucalypts within sight of their homes.
Authorities said some of the fires were creating their own weather conditions - pyrocumulus clouds that enveloped entire towns.
Meanwhile, high winds flung embers and burnt debris far ahead of the fires' front lines, depositing the dangerous detritus on the balconies and front yards of unsuspecting residents.
Firefighters moved from spot to spot trying to put out small fires caused by the falling debris.