Temperatures hit 21 degrees Celsius in Alert, Canada on Sunday - its average daily temperature in July is only 3 degrees.
We spoke to the 19-year-old about suing the US government for the climate emergency, and how he empowers his people through song.
In the wake of Sunday's climate march, Legco member Chu Hoi-dick will ask the Environment Secretary how far the city will go to address climate change.
The bad weather, coupled with the late announcement, amounted to a lower turnout.
Protests were expected to be held in more than 1,600 places in 110 countries. The Hong Kong march will take place on Sunday.
Protest organisers are asking citizens to walk out of work ahead of a crucial United Nations summit and demand immediate action.
Protests in more than 1,400 cities expected to attract more than the 1.4 million people who took part on March 15 - but won't include Hong Kong students.
The international movement organised a protest in London last month where more than 1,000 environmental activists were arrested.
The TV scientist appeared on political satire programme 'Last Week Tonight' to berate people who refuse to act on climate change.
A miscommunication meant student organisers cancelled march; they now hope to be able to protest this month.