It was just one night, but still most people in the city could not go without air conditioning.
On Wednesday, about 50,000 households switched off their air-con units for Hong Kong's first No Air Con Night, an event organised by the eco-group Green Sense to raise awareness of the environmental impact of air conditioning.
But for the remaining 2,285,000 homes in the city, it was business as usual.
'I tried to sleep without the A/C on, but it was too noisy to keep the windows open, and the room heated up so fast,' one Mong Kok resident said.
In just a few decades, Hong Kong has evolved into an air-con-dependent city, with most people spending their days in housing estates, shopping malls and office towers that become furnaces without the cooling systems.
The dependence continues at night as temperatures soar in our high-rise, heat island homes. So much so that air conditioning accounts for 60 per cent of the city's power consumption in summer.
When it comes to air conditioning, we seem to have built ourselves into a corner. Now, some are looking for a way out.
'Even in the 1990s, schools were not air-conditioned, many buses had no air con and there were not as many shopping malls,' Green Sense project manager Gabrielle Ho said. 'Now the first thing people do when they get home is switch on the air con. Everywhere is so air-conditioned, people have got used to it.'
Given that Hong Kong's average temperature is rising by as much as 0.6 degrees Celsius per decade - more than three times the world average - it's not hard to see why air-conditioning has become ubiquitous.
One of the most noticeable effects of the rise in temperatures is the higher frequency of hot nights, when the mercury does not dip below 28 degrees. In the early 1950s, there were no such nights, according to the Hong Kong Observatory. Now there are more than 20 per year.
Much of this is due to the urban heat island effect, a phenomenon in which materials such as concrete and asphalt absorb heat during the day and release it at night. Hong Kong's densely packed high-rises aggravate the problem, creating a 'wall effect' that reduces air circulation in many neighbourhoods. But excessive air-conditioning is also a big reason for the climbing temperatures.
Many Hong Kong residential buildings are designed so that air-conditioning units are as little as 10 centimetres from the living rooms of adjacent flats.
More than half the city's residents switch on their air conditioners because their neighbours' air-con units blow hot air directly into their flats, according to a Green Sense study released last week.
'It's a vicious cycle, because the more we use air-conditioning, the hotter it gets, and the more we need to use it,' said Angela Tam, the author of Sustainable Building in Hong Kong, which outlines how the city can develop in a more environmentally friendly way. 'You can't just talk about air-conditioning, you have to talk about the whole urban form. Given the way Hong Kong is built, there's no way for heat to disperse.'
That wasn't always the case.
'If you look at colonial Hong Kong, there were all sorts of things that were intended to cool the city,' Jonathan Solomon, an assistant professor of architecture at the University of Hong Kong, said. Streets were often lined with big trees, pavements were covered by arcades, and apartments had high ceilings, large windows and deep verandahs that could be shaded by bamboo screens.
'Now it's hotter outside and colder inside than it ever was before,' Solomon said. His latest research project looks at the interconnected interior spaces built throughout the city that make it possible to travel from a Central office to a home in Tseung Kwan O by MTR without setting foot outdoors.
'It's a new form of urban fabric that has arisen because of the ubiquity of air conditioning,' he said.
'In Hong Kong, it's so violently air- conditioned I have to keep a sweater around all summer long.'
Wan Chai-based architect David Erdman is working on a more sustainable approach.
Instead of 'the barnacles of air-conditioning units all over the place' Erdman and his partner Clover Lee try to reduce the need for air conditioning by integrating designs and materials that keep homes cool in hot weather.
'It's one of the first things we think about,' he said. 'Sustainability at this point is a fact, like structural engineering.
'It has to happen.'
Other architects, like Eric Schuldenfrei and Marisa Yiu, who run the design firm eskyiu, have also considered ways to reduce Hong Kong's dependence on air-conditioning.
'It's crazy these days because architects no longer learn how to design a building that ventilates naturally,' Schuldenfrei said. The pair are working on a concept for an Aberdeen tower that would cool itself using greenery and seawater.
But old habits die hard.
'Everyone wants a comfortable environment - that's the first thing on their minds,' Erdman said. And for now, air-conditioning remains the preferred way for people in Hong Kong to stay cool.
Only two senior government officials took part in No Air Con Night - Environment Secretary Edward Yau Tang-wah and Hong Kong Observatory director Dr Lee Boon-ying - even though the government has long promoted the use of energy-efficient air- conditioning systems.
The administration also maintains a temperature of no less than 25.5 degrees in its offices and encourages - but does not require - others to do the same.
Other governments around Asia, the world's fastest-growing market for air-conditioning, have taken a more aggressive stance against excessive air-con use.
In June, Taipei's municipal government banned businesses from setting their air conditioners to less than 26 degrees and threatened fines of up to HK$12,400 for non-compliance.
'What we really need to talk about is changing our lifestyles,' Lee said. 'I always encourage people to use electric fans but some don't even own them any more.'
He said the only way to really make things better was to use less air- conditioning, wear appropriate summer clothing and spend more time outdoors.
Even then, things are going to get worse before they get better. The Observatory predicts that the annual number of hot nights will increase from 20 a year today to more than 55 by 2029.
'If that's the case, our use of air- conditioning will only increase,' Lee said. 'We don't see any signs of improvement.'