Data story: Climate comparison between Hong Kong, London, Sydney and Toronto

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Because of the ongoing social unrest, more and more Hong Kong people want to move to other countries. According to a recent survey, most people who want to migrate are interested in relocating to Canada or Australia. After the United Kingdom eased immigration rules for Hong Kong residents in July 2020, many Hong Kong people are also considering moving to the United Kingdom. When moving to a different city, climate is often an important factor to consider. In this data story, we will compare the climate of Hong Kong with three popular emigration destinations, namely London in the United Kingdom, Sydney in Australia, and Toronto in Canada, using monthly meteorological normals data of the four cities from 1981-2010 retrieved from government website. We will analyze which city is the best for Hong Kong people to emigrate based on the climate.

Temperature

Hong Kong, as a subtropical city, has the highest mean temperature around the year, ranging from mean daily minimum at 14.5°C during January, to mean daily maximum at 31.4°C during July. The temperature difference between the day and night is the smallest, as shown in the table, the gap between maximum and minimum temperatures in Hong Kong is the smallest of all four cities. 5 months of summer Hong Kong (May to September) has a higher temperature than the optimal room temperature range (18-24°C: green) (below 18°C: blue and above 24°C: red), which may cause heat related health risks without cooling intervention.

London, Sydney, and Toronto all have lower mean temperatures and larger ranges of temperature difference throughout the year when compared with Hong Kong. As shown in the table, the gap between mean daily minimum temperature and mean daily maximum temperature of the three cities are larger, indicating the temperature differences between the day and night in these three cities are higher than Hong Kong. People living in these cities would need to prepare extra clothing to accommodate temperature differences when going out. It is worth noting that the lowest minimum temperature of Toronto during December to March is below 0°C, which may pose huge challenges to accommodate.

London and Toronto have 12 months and 11 months of mean daily minimum temperature lower than the room temperature, which shows that the nights of these two cities are relatively cold, which is harmful to health without proper insulation practices. Sydney citizens, on the other hand, can enjoy 4 months of comfortable nights (December to March) where the mean daily minimum temperature is within room temperature.

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Sunshine

Lack of sunshine is related to multiple health issues, ranging from vitamin D insufficiency to higher suicide rates. Fig. 2a & 2b shows London has the least sunshine throughout the year at only 1540 hours per year, following Hong Kong and Toronto at 1836 and 2066 hours per year respectively. Sydney has the most sunshine per year at 2593 hours. Sydney also has the most even hours of sunshine throughout the year, ranging from 176.7 hours in May to 246.0 hours in November. Toronto has the most uneven hours of sunshine throughout the year, ranging from a minimum of 78.1 hours in December, to 279.6 hours in July. 6 months (September to February) of London have the least amount of sunshine compared to other countries, meaning London citizens will have the longest period of time not being able to enjoy sunshine, and the positive health effects it brings.

Fig. 2a Sunshine

Fig. 2b Sunshine (annual)

Rainy days and rainfall

Rainy days, especially days with heavy rainfall, would pose difficulties for transportation, and sometimes cause floods. For amounts of rainfall throughout the year, Fig. 3a & 3b shows Hong Kong has significantly higher rainfall than the other three countries at 2,399 yearly, and most of the heavy rainfalls occur during summer (May to September). London, Sydney and Toronto all have relatively even amounts of rainfall throughout the year. This indicates that Hong Kong is most likely to suffer from heavy rains and people have to travel through rainy weathers throughout most of the summer.

Fig. 3a Rainfall

Fig. 3b Rainfall (annual)

Days of rainfall

As shown in Fig. 4a & 4b, Hong Kong has the highest number of rainy days throughout the year at 137.63, followed by London and Toronto, with Sydney being the city with least rainy days at 98.30. Hong Kong has notably more rainy days throughout the summer (May to September), London, Sydney have relatively even numbers of rainy days throughout the year, while Toronto have less rainy days during the winter (December to February).

Fig. 4a Days of Rainfall

Fig. 4b Days of Rainfall (annual)

Conclusion

Out of all three popular cities for emigration destinations, Sydney has the most comfortable temperature, most sunshine, least rainy days, and even amount of rainfall throughout the year. These factors make Sydney the best city to relocate in terms of climate. While Toronto has more sunlight and less rains compared to Hong Kong, new immigrants may face challenges in overcoming the cold temperature during its winters. London, while being slightly warmer than Toronto in the winter, has the least sunshine and second-most rainy days among the four cities, which means new immigrants have to adapt to the gloomy climate if they choose to relocate to London. Overall, Hong Kong people would enjoy fewer rainy days and less heavy rainfalls if they choose to move to either of the three popular cities, including the rumored “Rainy London”.