Skip Content

The Weather of July 2024 - An exceptionally hot July

2 August 2024

With a stronger than usual subtropical ridge dominating over southern China for most of the time in the month, July 2024 was exceptionally hot in Hong Kong.  The monthly mean minimum temperature of 28.0 degrees, monthly mean temperature of 29.9 degrees and monthly mean maximum temperature of 32.4 degrees were respectively 1.1 degrees, 1.0 degrees and 0.8 degrees above their normals and respectively one of the third, the fourth and one of the ninth highest on record for July.  The monthly rainfall was 458.5 millimetres, about 19 percent above the normal of 385.8 millimetres.  The accumulated rainfall recorded in the first seven months of the year was 1321.9 millimetres, about 10 percent below the normal figure of 1468.2 millimetres for the same period.

Under the influence of a southwesterly airstream, there were sunny intervals and a few showers in Hong Kong on the first two days of the month.  With the dominance of the subtropical ridge, apart from a few showers and isolated thunderstorms, there was a spell of generally fine and very hot weather in Hong Kong during 3 – 11 July.  The daily mean temperature of 30.8 degrees and daily minimum temperature of 29.2 degrees on 6 July were both the highest on record for Moderate Heat.  Moreover, the daily maximum temperature of 34.0 degrees on the same day was one of the highest on record for Moderate Heat.  With plenty of sunshine, the temperatures at the Observatory rose to a maximum of 34.8 degrees on the afternoon of 7 July, the highest of the month.  Furthermore, it was extremely hot on the afternoons of 7 and 10 July with maximum temperatures reaching 35 degrees or above in many places.  With the slight weakening of the subtropical ridge, there were generally more showers during 12 – 14 July.  Despite the extremely hot weather on 14 July, heavy showers and squally thunderstorms affected Hong Kong around that evening.  Over 50 millimetres of rainfall were recorded over Kwai Tsing and parts of Kowloon and Hong Kong Island.

Under the influence of a broad trough of low pressure over the South China Sea, local weather was a mixture of sunny intervals, showers and squally thunderstorms on 15 – 19 July.  More than 70 millimetres of rainfall were generally recorded over most parts of the territory and rainfall even exceeded 140 millimetres over Sha Tin, Wong Tai Sin and Kowloon City Districts on these five days.   Under the rain, the temperature at the Observatory dropped to a minimum of 26.0 degrees on 16 July, the lowest of the month.  While Hong Kong was still affected by a few showers and isolated thunderstorms on 20 July, the weather improved with very hot weather and sunny intervals under the influence of the subtropical ridge.

Meanwhile, the Inter-tropical Convergence Zone to the south of the subtropical ridge became active and favoured the formation of tropical cyclones.  An area of low pressure over the central part of the South China Sea intensified into a tropical depression on the afternoon of 19 July and tracked west-northwestwards towards Hainan Island.  The tropical depression intensified into a tropical storm and was named Prapiroon on the morning of 21 July.  Prapiroon further intensified and moved across Hainan Island and Beibu Wan on 21 – 22 July.  It then moved into the inland areas of the northern part of Vietnam and progressively weakened into an area of low pressure on 23 July.  The outer rainbands of Prapiroon brought a few squally showers and thunderstorms to Hong Kong on 21 July.  With Prapiroon departing from Hong Kong, it was very hot with sunny periods during the day on 22 July.

Besides, another area of low pressure over the seas east of the Philippines intensified into a tropical depression on 19 July.  It intensified into a tropical storm and was named Gaemi on 20 July.  Gaemi progressively intensified into a super typhoon in the next four days and headed towards Taiwan.  Moving generally northwestwards, Gaemi swept across Taiwan and then Fujian on 25 July.  It then moved into the inland areas of eastern China and central China and weakened into an area of low pressure over Hubei on 28 July.  Under the influence of the outer subsiding air of Gaemi, local weather was very hot with sunny periods on 23 – 25 July.  The daily minimum temperatures of 29.1 degrees and 29.7 degrees at Ta Kwu Ling and Sheung Shui respectively on 25 July were the highest on record for those stations.  Affected by an active southwest monsoon over the South China Sea, local winds strengthened later on 25 July and at first on 26 July.  Besides, the thundery showers triggered by high temperatures affected Hong Kong on the early morning of 26 July.  More than 60 millimetres of rainfall were recorded over the northern part of the New Territories.

Affected by an active southwest monsoon and the subsequent broad trough of low pressure over the northern part of the South China Sea, it was mainly cloudy with occasional heavy showers and squally thunderstorms on 27 – 31 July.  More than 150 millimetres of rainfall were generally recorded over most parts of the territory and rainfall even exceeded 250 millimetres over parts of the eastern territory on these five days.

Three tropical cyclones occurred over the South China Sea and the western North Pacific in July 2024.

Details of issuance and cancellation of various warnings/signals in the month are summarised in Tables 1.1 to 1.5.  Monthly meteorological figures and departures from normal for July are tabulated in Table 2.
 

Warnings and Signals issued in July 2024

Table 1.1   Tropical Cyclone Warning Signals
Name of
Tropical Cyclone
Signal
Number
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
PRAPIROON 1 20 / 7 2240 22 / 7 1220


Table 1.2   Strong Monsoon Signal
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
25 / 7 1645 26 / 7 1445


Table 1.3   Rainstorm Warning Signals
Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Amber 14 / 7 1900 14 / 7 2135
Amber 16 / 7 0535 16 / 7 0725
Amber 18 / 7 1345 18 / 7 1600
Amber 27 / 7 0900 27 / 7 1250
Amber 28 / 7 0550 28 / 7 1040
Amber 31 / 7 0735 31 / 7 1045


Table 1.4   Thunderstorm Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
1 / 7 0145 1 / 7 0345
4 / 7 0611 4 / 7 1120
4 / 7 1220 4 / 7 1530
6 / 7 1240 6 / 7 1400
7 / 7 1440 7 / 7 1515
8 / 7 1150 8 / 7 1430
9 / 7 1450 9 / 7 1615
10 / 7 0248 10 / 7 0730
11 / 7 1300 11 / 7 1400
11 / 7 1520 11 / 7 1630
12 / 7 0455 12 / 7 0700
12 / 7 0750 12 / 7 1430
13 / 7 0600 13 / 7 0830
13 / 7 1240 13 / 7 1400
14 / 7 1620 15 / 7 0130
15 / 7 0220 15 / 7 0400
15 / 7 0515 15 / 7 1030
15 / 7 1500 15 / 7 1930
15 / 7 1952 16 / 7 0045
16 / 7 0440 16 / 7 1300
16 / 7 1506 16 / 7 1730
16 / 7 1838 16 / 7 1945
17 / 7 0405 17 / 7 0745
17 / 7 1610 17 / 7 1830
18 / 7 0437 18 / 7 0615
18 / 7 0914 18 / 7 1700
18 / 7 1745 18 / 7 1820
19 / 7 0630 19 / 7 1430
20 / 7 0910 20 / 7 1230
20 / 7 1635 20 / 7 1800
21 / 7 1044 21 / 7 1300
21 / 7 2143 21 / 7 2300
22 / 7 1751 22 / 7 1900
25 / 7 1928 26 / 7 1030
26 / 7 1750 26 / 7 1930
27 / 7 0750 27 / 7 2000
27 / 7 2205 28 / 7 1230
28 / 7 1835 28 / 7 1920
29 / 7 0140 29 / 7 0430
29 / 7 1110 29 / 7 1630
29 / 7 2114 29 / 7 2200
30 / 7 0110 30 / 7 0630
31 / 7 0115 31 / 7 0245
31 / 7 0640 31 / 7 1630


Table 1.5   Very Hot Weather Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
1 / 7 0830 14 / 7 1845
15 / 7 1415 15 / 7 1730
17 / 7 1400 17 / 7 1640
20 / 7 1300 20 / 7 1800
22 / 7 1315 25 / 7 2000


Table 2   Figures and Departures from Normal - July 2024
Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 32.4 degrees C 0.8 degrees above normal
Mean Air Temperature 29.9 degrees C 1.0 degrees above normal
Mean Daily Minimum Air Temperature 28.0 degrees C 1.1 degrees above normal
Mean Dew Point Temperature 26.2 degrees C 1.0 degrees above normal
Mean Relative Humidity 81 % normal
Mean Cloud Amount 78 % 6 % above normal
Total Rainfall 458.5 mm 72.7 mm above normal
Number of hours of Reduced VisibilityΔ 0 hour 11.2 hours below normal§
Total Bright Sunshine Duration 178.3 hours 19.0 hours below normal
Mean Daily Global Solar Radiation 17.00 Megajoule / square metre 0.22 Megajoule below normal
Total Evaporation 113.6 mm 28.4 mm below normal


  Remarks : All measurements were made at the Hong Kong Observatory except sunshine, solar radiation and evaporation which were recorded at King's Park Meteorological Station and visibility which was observed at the Hong Kong International Airport.

  Δ

The visibility readings at the Hong Kong International Airport are based on hourly observations by professional meteorological observers in 2004 and before, and average readings over the 10-minute period before the clock hour of the visibility meter near the middle of the south runway from 2005 onwards. The change of the data source in 2005 is an improvement of the visibility assessment using instrumented observations following the international trend.
Before 10 October 2007, the number of hours of reduced visibility at the Hong Kong International Airport in 2005 and thereafter displayed in this web page was based on hourly visibility observations by professional meteorological observers. Since 10 October 2007, the data have been revised using the average visibility readings over the 10-minute period before the clock hour, as recorded by the visibility meter near the middle of the south runway.


  *   Departure from 1991 - 2020 climatological normal, except for number of hours of reduced visibility

  §   Departure from mean value between 1997 and 2023

Daily values of selected meteorological elements for Hong Kong for July 2024
The percentile map of mean temperature of July 2024

  Remarks : Extremely high: above 95th percentile
Above normal: between 75th and 95th percentile
Normal: between 25th and 75th percentile
Below normal: between 5th and 25th percentile
Extremely low: below 5th percentile
Percentile and 5-day running average values are
computed based on the data from 1991 to 2020


Extract of Meteorological Observations in Hong Kong for July 2024