The Weather of July 2024 - An exceptionally hot July
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
Name of Tropical Cyclone |
Signal Number |
Beginning Time | Ending Time | ||
---|---|---|---|---|---|
Day/Month | HKT | Day/Month | HKT | ||
PRAPIROON | 1 | 20 / 7 | 2240 | 22 / 7 | 1220 |
Beginning Time | Ending Time | ||
---|---|---|---|
Day/Month | HKT | Day/Month | HKT |
25 / 7 | 1645 | 26 / 7 | 1445 |
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 |
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 |
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 |
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. |
* Departure from 1991 - 2020 climatological normal, except for number of hours of reduced visibility |
|
§ Departure from mean value between 1997 and 2023 |
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