2 August 2023

With a stronger than usual subtropical ridge dominating over southern China for most of the time in the month, July 2023 was exceptionally hot in Hong Kong. The monthly mean maximum temperature of 33.0 degrees, monthly mean temperature of 30.1 degrees and monthly mean minimum temperature of 28.0 degrees were respectively 1.4 degrees, 1.2 degrees and 1.1 degrees above their normals and all were the third highest on record for July. The month was also much drier than usual with only 175.2 millimetres of rainfall, about 45 percent of the normal of 385.8 millimetres. The accumulated rainfall recorded in the first seven months of the year was 1016.5 millimetres, about 31 percent below the normal figure of 1468.2 millimetres for the same period.

Under the influence of a broad trough of low pressure and the subsequent southwesterly airstream, the weather of Hong Kong was mainly cloudy with occasional showers and squally thunderstorms on the first four days of the month. More than 40 millimetres of rainfall were recorded over most parts of the territory and rainfall even exceeded 100 millimetres over Tai Po, Sha Tin and parts of Lantau Island on these four days. Under the rain, temperatures at the Observatory dropped to a minimum of 26.2 degrees on 1 and 2 July, the lowest of the month. Dominated by an anticyclone aloft, apart from isolated showers, local weather turned generally fine and very hot on 5 July and remained so till 14 July. It was also extremely hot on the afternoons of 13 - 14 July with maximum temperatures reaching 35 degrees or above in many places.

Meanwhile, an area of low pressure near northern Luzon intensified into a tropical depression on 14 July and later named as Talim. It tracked west-northwestwards across the northern part of the South China Sea towards the coast of western Guangdong and intensified into a typhoon gradually on 15 – 17 July. Talim moved across Leizhou Peninsula and Beibu Wan on the night of 17 July and the next morning. It then moved into the inland areas of Guangxi on 18 July and eventually weakened into an area of low pressure over the northern part of Vietnam on 19 July.

Under the influence of the outer subsiding air of Talim, it was mainly fine and extremely hot during the day on 15 July. Squally thunderstorms triggered by high temperatures also affected parts of the territory later on that day. With Talim edging closer to the western Guangdong and further intensifying, local winds strengthened gradually with occasional squally showers and thunderstorms on 16 July. Strong to gale force winds generally affected the territory with occasional storm force winds on high ground on 17 July, necessitating the issuance of the first No.8 Gale or Storm Signal this year. As Talim departed from Hong Kong and weakened over inland, local winds moderated gradually later on 17 July and the next day. The outer rainbands of Talim brought occasional heavy squally showers to Hong Kong on 17 – 18 July. More than 40 millimetres of rainfall were generally recorded over most parts of the territory on these two days and rainfall even exceeded 90 millimetres in parts of Tai Po and North Districts.

Under the influence of a broad trough of low pressure, the weather was mainly cloudy with a few showers on 19 July. Affected by an anticyclone aloft, apart from a few showers, generally fine and very hot weather persisted in Hong Kong on 20 – 25 July. It was extremely hot on the afternoons of 24 - 25 July with maximum temperatures reaching 35 degrees or above in many places. Meanwhile, tropical cyclone Doksuri moved across the Luzon Strait and entered the northeastern part of the South China Sea on 26 – 27 July. It then moved north-northwestwards across the northeastern part of the South China Sea and made landfall over Jinjiang, Fujian on 28 July.

Under the influence of the outer subsiding air of Doksuri, it was generally fine and extremely hot during the day on 26 - 27 July. The maximum temperature at the Observatory soared to 36.1 degrees on the afternoon of 27 July, the highest of the month and one of the highest monthly absolute maximum temperatures on record for July. Moreover, the daily mean temperature on that day was 32.2 degrees and the highest on record for July. The oppressive heat also triggered squally thunderstorms on that evening. It was very hot with sunny periods and isolated showers on 28 July. Affected by an active southerly airstream, the weather turned showery with squally thunderstorms on 29 – 30 July. More than 40 millimetres of rainfall were recorded over most parts of the territory and rainfall even exceeded 100 millimetres over parts of Tai Po, Sha Tin, Tuen Mun and North Districts in these two days. Under the influence of a broad trough of low pressure, it was showery with thunderstorms in the small hours of 31 July. The weather improved with sunny periods during the day.

Three tropical cyclones occurred over the South China Sea and the western North Pacific in July 2023.

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