Summer Weather in Hong Kong Hong Kong SAR China

Daily high temperatures are around 88°F, rarely falling below 81°F or exceeding 94°F. The highest daily average high temperature is 90°F on July 24.

Daily low temperatures are around 80°F, rarely falling below 75°F or exceeding 84°F. The highest daily average low temperature is 82°F on July 9.

For reference, on July 23, the hottest day of the year, temperatures in Hong Kong typically range from 82°F to 90°F, while on January 23, the coldest day of the year, they range from 57°F to 66°F.

The figure below shows you a compact characterization of the hourly average summer temperatures. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

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The summer in Hong Kong experiences decreasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy decreasing from 84% to 74%. The highest chance of overcast or mostly cloudy conditions is 85% on June 11.

The clearest day of the summer is August 31, with clear, mostly clear, or partly cloudy conditions 26% of the time.

For reference, on June 11, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 85%, while on January 4, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 74%.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Hong Kong, the chance of a wet day over the course of the summer is rapidly decreasing, starting the season at 53% and ending it at 46%.

For reference, the year's highest daily chance of a wet day is 54% on June 16, and its lowest chance is 7% on December 18.

Rainfall

To show variation within the season and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during the summer in Hong Kong is rapidly decreasing, starting the season at 9.3 inches, when it rarely exceeds 15.7 inches or falls below 3.5 inches, and ending the season at 8.0 inches, when it rarely exceeds 13.3 inches or falls below 2.8 inches.

The highest average 31-day accumulation is 9.7 inches on June 9.

Over the course of the summer in Hong Kong, the length of the day is decreasing. From the start to the end of the season, the length of the day decreases by 49 minutes, implying an average daily decrease of 33 seconds, and weekly decrease of 3 minutes, 48 seconds.

The shortest day of the summer is August 31, with 12 hours, 35 minutes of daylight and the longest day is June 20, with 13 hours, 30 minutes of daylight.

The earliest sunrise of the summer in Hong Kong is 5:38 AM on June 7 and the latest sunrise is 27 minutes later at 6:05 AM on August 31.

The latest sunset is 7:11 PM on July 4 and the earliest sunset is 30 minutes earlier at 6:40 PM on August 31.

Daylight saving time is not observed in Hong Kong during 2024.

For reference, on June 20, the longest day of the year, the Sun rises at 5:40 AM and sets 13 hours, 30 minutes later, at 7:09 PM, while on December 21, the shortest day of the year, it rises at 6:58 AM and sets 10 hours, 46 minutes later, at 5:44 PM.

The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation.

The figure below presents a compact representation of key lunar data for the summer of 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The chance that a given day will be muggy in Hong Kong is gradually increasing during the summer, rising from 97% to 99% over the course of the season.

The highest chance of a muggy day during the summer is 100% on July 29.

For reference, on July 11, the muggiest day of the year, there are muggy conditions 100% of the time, while on January 15, the least muggy day of the year, there are muggy conditions 2% of the time.

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Hong Kong is gradually decreasing during the summer, decreasing from 10.1 miles per hour to 9.3 miles per hour over the course of the season.

For reference, on December 8, the windiest day of the year, the daily average wind speed is 12.8 miles per hour, while on August 19, the calmest day of the year, the daily average wind speed is 9.1 miles per hour.

The highest daily average wind speed during the summer is 11.0 miles per hour on June 20. The lowest daily average wind speed during the summer is 9.1 miles per hour on August 19.

The wind direction in Hong Kong during the summer is predominantly out of the south from June 1 to August 28 and the east from August 28 to August 31.

Hong Kong is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.

The average surface water temperature in Hong Kong is gradually increasing during the summer, rising by 3°F, from 80°F to 83°F, over the course of the season.

The highest average surface water temperature during the summer is 84°F on August 17.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

Temperatures in Hong Kong are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

The average accumulated growing degree days in Hong Kong are very rapidly increasing during the summer, increasing by 3,069°F, from 2,961°F to 6,030°F, over the course of the season.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy in Hong Kong is essentially constant during the summer, remaining within 0.2 kWh of 4.9 kWh throughout.

The lowest average daily incident shortwave solar energy during the summer is 4.7 kWh on August 19.

For the purposes of this report, the geographical coordinates of Hong Kong are 22.250 deg latitude, 114.167 deg longitude, and 0 ft elevation.

The topography within 2 miles of Hong Kong is essentially flat, with a maximum elevation change of 0 feet and an average elevation above sea level of 0 feet. Within 10 miles is also essentially flat (0 feet). Within 50 miles is also essentially flat (0 feet).

The area within 2 miles of Hong Kong is covered by water (35%), trees (31%), and artificial surfaces (25%), within 10 miles by water (69%) and artificial surfaces (19%), and within 50 miles by water (74%) and trees (12%).