At least 35,000 people nationwide - and perhaps as many as 225,000 - are set to strike in favour of stronger action on climate change.
The Global Strike 4 Climate will on Friday take place in 110 towns and cities across Australia, with organisers demanding government and business commit to a target of net zero carbon emissions by 2030.
They are also campaigning for a transition to 100 per cent renewable energy.
"Australia is already on the frontlines of the climate crisis. Prolonged drought. Flash flooding. Catastrophic bushfires, severe cyclones and heatwaves," Australian strike organisers say on their Facebook event page.
"But just at the time when we need to ramp up climate solutions, we have elected a government that wants to open the floodgates to new coal, oil and gas projects that put all of us at risk."
While about 37,000 people have confirmed their attendance at capital city rallies on the strike's Facebook pages, a Global Strike 4 Climate spokeswoman said organisers expect a 50 per cent increase on the attendance of the most recent climate strike in March, which garnered 150,000 protesters.
Universities have confirmed they will not penalise students for attending the rallies, while the Uniting Church synod for NSW and the ACT have backed their students to attend the demonstrations.
But Catholic and Anglican church-run schools say their students should remain in class, as do NSW public schools.
Some Queensland students have called for Adani to halt their Carmichael coal mine, and for a ban on new coal, oil and gas projects.
The Australian Council of Trade Unions supported the strike.
"One of the fundamentals of unionism is the power of people joining together to stand up for justice. We have and must take a stand for our future when our government will not," the ACTU said in a statement.
The strike is the latest in a worldwide movement started in August 2018 when 16-year-old Swedish climate activist Greta Thunberg began protesting outside Sweden's parliament on school days.
She'll participate in the UN's youth climate forum on Saturday and address world leaders at the UN secretary general's climate summit on September 23.
She is currently in the US after taking a yacht across the Atlantic to prevent carbon emissions, and urged US lawmakers to "listen to the scientists".
A second global strike is scheduled for September 27.
Australian Associated Press