The persistent wave of high temperatures in Hong Kong has once again brought into focus the impact of adverse climatic events and the predicament of residents living in tightly packed places.

According to the Hong Kong Observatory (HKO), over the past 100 years or so, the numbers of hot nights, which it describes as days in Hong Kong with a minimum temperature of 28 C or above, and very hot days as days with a maximum temperature of 33 C or above, have increased while the number of cold days, described as days with a minimum temperature of 12 C or below, has decreased. If we look at the past decade’s HKO data, there were 28 very hot days in 2015; 38 in 2016; 29 in 2017; 36 in 2018; 33 in 2019; 47 in 2020; 54 in 2021; 52 in 2022; 54 in 2023 and 52 in 2024. Clearly, the rise in very hot days has been dramatic since 2020. In 2025, Hong Kong saw one very hot day each in April and May and six in June. Last year, the highest annual temperature recorded was 35.7 C. In 2021, 2022 and 2023, it was 36.1 C. Even for climate skeptics, the data could not be more compelling.

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With a high concentration of buildings, Hong Kong experiences the “urban heat island” (UHI) effect, which makes the urban area significantly warmer than the surrounding areas. According to the World Bank, data indicate that for the world’s largest cities, productivity losses from the UHI effect and global warming will decrease real gross domestic product by 1.4 to 1.7 percent for the median city by 2050.

An International Monetary Fund (IMF) report published in January points out that the annual mean temperature in Hong Kong rose by 0.14 C per decade from 1885 to 2023. “The rise accelerated to 0.30 C per decade during the period from 1994 to 2023, with projected increases ranging from about 1.2 to 3.6 degrees Celsius under different greenhouse gas emission scenarios by 2100.” The IMF echoes a wide consensus when it says this poses risks to human health and escalates energy consumption from cooling.

In the first week of July, two studies published by the Society for Community Organization indicated that temperatures in substandard housing in Hong Kong climbed to as high as 40 C as July opened. Additionally, it was reported that 40 percent of tenants living in such accommodations reported having poor-quality windows or no windows at all. According to the organization, as widely reported, 72 percent of such tenants surveyed worried that the rising heat would put a dent on their finances amid reduced income and subsidies, while 68 percent anticipated higher utility bills.

Hong Kong’s substandard housing is synonymous with the infamous subdivided units (SDUs) that authorities are currently on a legislative path to regulate. Officially defined as structures “formed by splitting a unit of quarters into two or more ‘internally connected’ and ‘externally accessible’ units commonly for rental purposes”, they are largely perceived as crammed, hazardous and unhygienic, and seen as the last resort for tens of thousands on the lowest rung of the private-rental housing ladder.

The units are primarily rented out to a low-income cohort with a median monthly income assessed at HK$14,000 ($1,783) in 2021 when the median monthly income of the whole working population stood at HK$19,500. In other words, a dramatically disadvantaged section of Hong Kong residents is the primary occupant of SDUs.

Let’s take a look at absolute numbers.

According to 2021 census data, 34,000 children lived in SDUs. Yes, 34,000 children from low-income families growing up on average in less than 80 square feet (7.4 square meters) of living space, often lacking a separate toilet and an external window. Occupants of these units aged 65 and above numbered 21,500. The 2021 Population Census recorded some 108,200 SDUs in Hong Kong accommodating 107,400 households and 215,700 people. If we look at the numbers, a lot more people were living in SDUs in 2021 as compared to 2016. The 2016 census had enumerated 92,700 SDUs in Hong Kong, accommodating 91,800 households and 209,700 people.

2021 was also the year the Hong Kong Special Administrative Region government announced Climate Action Plan 2050, which earmarked four major decarbonization strategies: “net-zero electricity generation”; “energy saving and green buildings”; “green transport” and “waste reduction”, with the aim to attain carbon neutrality before 2050. While Hong Kong’s carbon emissions have been seen as decreasing since 2014, authorities aim at 26 to 36 percent absolute reduction and a reduction to 3.3 to 3.8 metric tons on a per capita basis.

In 2023, the year when the highest recorded temperature was 36.1 C for the third year in a row, authorities introduced a new three-tier mechanism to protect outdoor workers from heatstroke. In terms of climate statistics, 2023 stands out. That was the year in which the third-highest annual mean maximum temperature of 27.2 C, the third-highest annual mean temperature of 24.5 C, and the second highest annual mean minimum temperature of 22.6 C were recorded.

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Also in 2023, Hong Kong recorded the highest hourly rainfall at 158.1 millimeters. The IMF quotes Insurance Authority data to cite that total claims incurred by Typhoon Saola and the black rainstorm in early September 2023 amounted to HK$1.9 billion — more than 80 percent of it related to property damages. As per the HKO’s annual outlook for 2025, five to eight tropical cyclones are expected to come within 500 kilometers of Hong Kong.

If heat is rising, extreme precipitation has become more frequent. To quote the HKO, “The hourly rainfall record at the Hong Kong Observatory Headquarters used to be broken once every few decades in the past. However, the record has been broken several times in the recent few decades.”

Widely swinging weather and its adverse effects are not academic considerations but constitute a hard-knock, bitter reality for a low-income minority in one of the world’s wealthiest cities. The minority that slips through the cracks, that lives in the shadows, that may not be hogging the headlines. The minority that, at last count, included 34,000 children who long for a window on the wall that looks out to the world. Yes, 34,000. And yes, they are waiting for a respite.

The author is an award-winning English-language fiction writer and current-affairs commentator.

The views do not necessarily reflect those of China Daily.