In total, 253 of Sweden's 290 municipalities took part in Saturday's event, the organization said on Tuesday.
This is a new record, amounting to 87 percent of the entire country, and an increase of ten municipalities from the previous year.
In addition to an hour of darkness as lights were turned off in homes, businesses and public buildings, many Swedish towns held events to raise awareness of issues affecting the future of the planet.
“Many municipalities got involved by organizing a torchlight procession, or by giving out candles to residents and encouraging them to turn off their electric lights during Earth Hour,” a WWF press spokesperson told The Local.
Other events ranged from vegetarian dinners to eco-fashion shows and climate seminars.
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Meanwhile, the youth wing of WWF Sweden ran a YouTube livestream with social media influencers, labelled as “pre-party hype” for the event.
“It is encouraging that so many municipalities got involved in everything, from action on climate change, recycling and reducing food waste to debates and exhibitions,” said Håkan Wirtén, Swedish Secretary General of the WWF.
A press officer from the organization told The Local that one of the reasons for Sweden's high rate of participation was that the WWF had been coordinating with municipalities for months in advance.
But another likely factor is that the idea of 'mys' – a kind of cosiness, usually characterized by spending winter evenings with family and friends – is ingrained in Swedish culture. Plenty of Swedes shared photos on social media of candlelit dinners, board game nights or movie evenings they had organized to mark Earth Hour.
In total, 187 countries across all seven continents participated in Earth Hour.
Over 3,000 iconic buildings and monuments switched off their lights, including the Paris Eiffel Tower, Sydney’s Opera House and the Colosseum in Rome.