Hong Kong's Climate Data
AdvancedObservatory data show Hong Kong has a subtropical climate — hot, humid summers and cool, dry winters — and spring fog forms as warm moist air meets cooler sea.
- Weather is short-term; climate is the average over years.
- Hong Kong is subtropical: hot humid rainy summers, cool dry winters.
- Describe climate with data: temperature, wind, humidity, rainfall.
文體小知識：說明文教你看懂數據。這一篇帶你閱讀天文台的月報，用數字說出香港氣候的故事。
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1The Hong Kong Observatory, over 140 years old, measures and publishes weather data every day. Weather is the state of the atmosphere over a short time, such as rain and wind today; climate is the average weather over many years. To know Hong Kong's climate, learn to read the data on temperature, wind, humidity and rainfall.
2Hong Kong lies in the subtropics with four clear seasons. Summers in July and August are hot and humid, averaging about 28 to 31 degrees Celsius; winters in January and February are cool and dry, about 15 to 18 degrees; spring and autumn are mild and pleasant. Thermometers take the readings, and data from Observatory headquarters and automatic stations draw Hong Kong's temperature map.
3Wind data include direction and strength. Direction means where the wind comes from: south-westerly winds prevail in summer, while the winter is shaped by the northeast monsoon; typhoons occasionally bring fierce winds and heavy rain between summer and autumn. Wind vanes and anemometers measure them. Relative humidity shows how much water vapour the air holds; in the humid spring it often tops 80%, beading walls and floors, while autumn is drier.
4Hong Kong's yearly rainfall is plentiful, averaging over 2,400 millimetres, measured by rain gauges. The wet season, May to September, brings about eighty percent of the year's rain, often with rainstorms and thunder; November to February is clearly drier. So Hong Kong's climate can be summarised: hot, humid and rainy summers; cool, dry winters.
5In spring Hong Kong occasionally sees thick fog, especially over the sea at dawn and near the airport. Fog forms like this: warm, moist air flows over cooler water, and its water vapour condenses on cooling into countless tiny droplets hanging in the air near the ground, lowering visibility. Fog is like a cloud, just one that hugs the ground.
6In the subtropics, snow and frost are rare: snow needs temperatures below zero degrees Celsius, and frost is ice crystals forming on surfaces near the ground. Hail, meanwhile, forms in storm clouds where droplets are swept repeatedly upward by strong currents and freeze; it appears mostly in spring and summer storms. Understanding why weather happens, we can admire the wonder of the atmosphere.
1Summary 重點摘要
Observatory data show Hong Kong has a subtropical climate — hot, humid summers and cool, dry winters — and spring fog forms as warm moist air meets cooler sea.
2Vocabulary cards Vocabulary
The atmosphere's state over a short time, such as rain or wind today.
The average weather of a place over many years.
How hot or cold the air is, measured with a thermometer in degrees Celsius.
The direction wind comes from, such as an east wind from the east.
How much water vapour the air holds, as a percentage; 100% means saturated.
The depth of rain fallen over a period, measured in millimetres.
The instrument that measures how much rain has fallen.
Tiny droplets hanging in air near the ground that lower visibility.
White ice crystals forming on surfaces when temperatures fall very low.
Little ice pellets formed in storm clouds before falling.
3Step by step Steps
- Step 1: Tell weather from climateWeather is the atmosphere over a short time — rain today, sunshine tomorrow, an easterly wind by afternoon; climate is a place's weather averaged over many years, such as Hong Kong's hot humid summers and cool dry winters. Weather changes daily; climate is fairly steady. The Observatory forecasts weather daily, and long-term averages form the climate. Tell the two apart first, and the data will never confuse you.
- Step 2: Describe Hong Kong's temperatures with dataReading Observatory data: Hong Kong's July average is about 28 to 31 degrees Celsius, topping 33 on the hottest days; January averages about 15 to 18, falling below 10 on the coldest. The yearly average is about 23 degrees — a subtropical climate. Describe temperature with months, averages and extremes: July's average of about 29 degrees is more scientific than just saying summer is very hot. The thermometer is the basic tool, and over a hundred automatic stations now cover the territory.
- Step 3: Read wind direction, strength and humidity dataWind direction uses eight or sixteen compass points: south-westerly winds prevail in summer, and the northeast monsoon rules winter. Strength is measured in kilometres per hour, reaching hurricane force when typhoons strike. Relative humidity is a percentage: in the humid spring it often tops 80%, beading walls and floors and keeping clothes damp; in autumn and winter it falls to about 50 to 60% and skin dries out. Wind vanes, anemometers and hygrometers take the measurements.
- Step 4: Analyse Hong Kong's rainfall dataHong Kong's yearly rainfall averages over 2,400 millimetres — a rainy city. Monthly reports show May to September is the wet season, with single months reaching four to five hundred millimetres, often with rainstorms and thunder; November to February usually bring only a few tens of millimetres each. Rain gauges measure depth in millimetres. The data remind us: guard against flooding and lightning in summer, and watch fire and dryness warnings in winter.
- Step 5: Understand how fog formsSpring often brings thick fog, especially over the sea at dawn and near the airport and hilltops. Here is the cause: spring seawater is still cool, and warm moist air from the south flows over it; the air cools, its vapour reaches saturation and condenses into countless tiny droplets hanging near the ground, cutting visibility below one kilometre — that is fog. Fog appears mostly at dawn and fades as the sun rises and the air warms; airports and bridges must make special arrangements in fog.
- Step 6: Know how snow, frost and hail formSnow forms high in the cloud where temperatures sit below zero Celsius, vapour turning straight into ice crystals that drift down; Hong Kong's winters rarely drop below 5 degrees, so snow is extremely rare, though high peaks like Tai Mo Shan may see frost on unusually cold days. Frost is white ice crystals forming on surfaces chilled below zero. Hail comes from storm clouds: droplets are swept up by strong rising air, freeze, ride up and down growing layers, and finally fall — mostly in spring and summer storms.
5Worked example Example
Example: An Observatory monthly report shows an average temperature of 29.1 degrees, average relative humidity of 83%, total rainfall of 430 millimetres, and prevailing south-westerly winds. Which season is this likely to be? Describe the month's climate using the data, and explain why the sea is often foggy on spring mornings.
- First the temperature: an average of 29.1 degrees is hot, matching Hong Kong's summer (June to September).
- Then humidity and rainfall: 83% relative humidity and 430 millimetres of rain are wet and humid — again summer features.
- Add the prevailing south-westerly wind, and all four data point to summer, so the conclusion is well founded.
- Describe the month: hot, humid and rainy with south-westerly winds — a typical Hong Kong summer month.
- Fog's cause: in spring, warm moist air flows over cooler seas, the vapour condenses into droplets hanging near the surface, forming thick fog.
- Answer: The data — 29.1 degrees, 83% humidity, 430 millimetres of rain and south-westerly winds — all match Hong Kong's summer, so the month is likely one of June to September. As for fog: in spring, warm moist air from the south flows over still-cool seas; the air cools and its vapour condenses into countless droplets hanging near the surface, slashing visibility and forming the thick morning fog over the sea.
6Common mistakes Mistakes
7Quick check Quick check
Q1What is the difference between weather and climate?
Q2Which months are Hong Kong's wet season?
Q3Which instrument measures rainfall?
Q4What does 100% relative humidity mean?
Q5How does fog form?
8Recap Recap
- Weather is short-term; climate is the average over years.
- Hong Kong is subtropical: hot humid rainy summers, cool dry winters.
- Describe climate with data: temperature, wind, humidity, rainfall.
- Spring fog: warm moist air over cooler sea condenses into droplets.
- Snow, frost and hail are rare here, tied to cold and storm clouds.