The Weather of December 2025 - An unseasonably mild December
5 January 2026
With the northeast monsoon over southern China generally weaker than normal for most of the time in the month, December 2025 was much warmer than usual in Hong Kong. The monthly mean maximum temperature of 22.4 degrees, monthly mean temperature of 20.2 degrees and monthly mean minimum temperature of 18.4 degrees were 2.0 degrees, 2.0 degrees and 2.2 degrees above their corresponding normals and all of them were the second highest on record for December. This was also the first time that no Cold Weather Warning was in force in November and December in a year since the Cold Weather Warning System commenced operation in 1999. The month was also drier than usual with a total rainfall of 6.5 millimetres, only about 23 percent of the normal of 28.8 millimetres. The annual total rainfall of 2558.7 millimetres was about 5 percent above the annual normal of 2431.2 millimetres.
With a band of clouds covering the coast of Guangdong, the weather of Hong Kong was mainly cloudy with one or two rain patches on the first four days of the month. Under the influence of a dry northeast monsoon, the weather turned generally fine and dry on 5 December and remained so on the following four days. With the return of a cloud band, it turned mainly cloudy with one or two rain patches on 10 December and the next morning. It turned generally fine during the day on 11 December as the clouds thinned out. With plenty of sunshine, the maximum temperature at the Observatory rose to 26.0 degrees that afternoon, the highest of the month. A fresh to strong easterly airstream affected the coast of Guangdong the next day. Locally, the weather remained mainly fine and dry.
A cold front moved across the coast of Guangdong on the late afternoon of 13 December. Under the influence of its associated strong northeast monsoon, winds strengthened from the north and temperatures fell progressively. It was rather cool on the mornings of the next two days. Besides, while there were one or two rain patches on 13 December under the influence of a broad band of clouds, the weather turned generally fine on the night of 14 December under the influence of a dry northeast monsoon and remained so on the next three days. It was also very dry on 14 – 15 December with the relative humidity over most parts of the territory staying around 30 – 40 percent during the day. With the return of a broad band of clouds, the weather became cloudier with one or two rain patches later on 18 December and the next day. With the thinning out of the cloud band, the weather turned generally fine and dry during the day on 20 December.
Under the influence of a fresh to strong northeast monsoon, it was windier on the following two days. While it was fine and dry on 21 December, the weather turned mainly cloudy on 22 December due to the approach of a cloud band and remained so on the following four days. While there were one or two rain patches on the morning of 25 December, with a replenishment of the northeast monsoon reaching the coast of Guangdong that morning, the local weather became dry and cool that day. It remained dry with rather cool mornings on the following two days, with the temperature at the Observatory falling to a minimum of 13.8 degrees on the morning of 27 December, the lowest of the month. Under the influence of the dry northeast monsoon, the local weather turned mainly fine on 27 – 29 December. With the moderation of the northeast monsoon, winds subsided on 30 December, with visibility falling below 5000 metres over parts of the territory that morning. An easterly airstream brought cloudier weather on the last day of the month.
Three tropical cyclones occurred over the South China Sea and the western North Pacific in December 2025.
Details of issuance and cancellation of various warnings/signals in the month are summarised in Tables 1.1 to 1.2. Monthly meteorological figures and departures from normal for December are tabulated in Table 2.
With the northeast monsoon over southern China generally weaker than normal for most of the time in the month, December 2025 was much warmer than usual in Hong Kong. The monthly mean maximum temperature of 22.4 degrees, monthly mean temperature of 20.2 degrees and monthly mean minimum temperature of 18.4 degrees were 2.0 degrees, 2.0 degrees and 2.2 degrees above their corresponding normals and all of them were the second highest on record for December. This was also the first time that no Cold Weather Warning was in force in November and December in a year since the Cold Weather Warning System commenced operation in 1999. The month was also drier than usual with a total rainfall of 6.5 millimetres, only about 23 percent of the normal of 28.8 millimetres. The annual total rainfall of 2558.7 millimetres was about 5 percent above the annual normal of 2431.2 millimetres.
With a band of clouds covering the coast of Guangdong, the weather of Hong Kong was mainly cloudy with one or two rain patches on the first four days of the month. Under the influence of a dry northeast monsoon, the weather turned generally fine and dry on 5 December and remained so on the following four days. With the return of a cloud band, it turned mainly cloudy with one or two rain patches on 10 December and the next morning. It turned generally fine during the day on 11 December as the clouds thinned out. With plenty of sunshine, the maximum temperature at the Observatory rose to 26.0 degrees that afternoon, the highest of the month. A fresh to strong easterly airstream affected the coast of Guangdong the next day. Locally, the weather remained mainly fine and dry.
A cold front moved across the coast of Guangdong on the late afternoon of 13 December. Under the influence of its associated strong northeast monsoon, winds strengthened from the north and temperatures fell progressively. It was rather cool on the mornings of the next two days. Besides, while there were one or two rain patches on 13 December under the influence of a broad band of clouds, the weather turned generally fine on the night of 14 December under the influence of a dry northeast monsoon and remained so on the next three days. It was also very dry on 14 – 15 December with the relative humidity over most parts of the territory staying around 30 – 40 percent during the day. With the return of a broad band of clouds, the weather became cloudier with one or two rain patches later on 18 December and the next day. With the thinning out of the cloud band, the weather turned generally fine and dry during the day on 20 December.
Under the influence of a fresh to strong northeast monsoon, it was windier on the following two days. While it was fine and dry on 21 December, the weather turned mainly cloudy on 22 December due to the approach of a cloud band and remained so on the following four days. While there were one or two rain patches on the morning of 25 December, with a replenishment of the northeast monsoon reaching the coast of Guangdong that morning, the local weather became dry and cool that day. It remained dry with rather cool mornings on the following two days, with the temperature at the Observatory falling to a minimum of 13.8 degrees on the morning of 27 December, the lowest of the month. Under the influence of the dry northeast monsoon, the local weather turned mainly fine on 27 – 29 December. With the moderation of the northeast monsoon, winds subsided on 30 December, with visibility falling below 5000 metres over parts of the territory that morning. An easterly airstream brought cloudier weather on the last day of the month.
Three tropical cyclones occurred over the South China Sea and the western North Pacific in December 2025.
Details of issuance and cancellation of various warnings/signals in the month are summarised in Tables 1.1 to 1.2. Monthly meteorological figures and departures from normal for December are tabulated in Table 2.
Warnings and Signals issued in December 2025
| Beginning Time | Ending Time | ||
|---|---|---|---|
| Day/Month | HKT | Day/Month | HKT |
| 12 / 12 | 0745 | 12 / 12 | 2030 |
| 13 / 12 | 1615 | 14 / 12 | 1130 |
| 22 / 12 | 0145 | 22 / 12 | 0745 |
| 25 / 12 | 1145 | 26 / 12 | 0445 |
| Colour | Beginning Time | Ending Time | ||
|---|---|---|---|---|
| Day/Month | HKT | Day/Month | HKT | |
| Yellow | 6 / 12 | 0600 | 6 / 12 | 2000 |
| Yellow | 7 / 12 | 0600 | 7 / 12 | 2130 |
| Red | 8 / 12 | 0600 | 8 / 12 | 2300 |
| Red | 14 / 12 | 0730 | 15 / 12 | 2245 |
| Red | 17 / 12 | 1110 | 17 / 12 | 1915 |
| Yellow | 20 / 12 | 0600 | 21 / 12 | 1730 |
| Red | 25 / 12 | 1130 | 26 / 12 | 2300 |
| Yellow | 27 / 12 | 0600 | 27 / 12 | 2230 |
| Yellow | 28 / 12 | 0730 | 28 / 12 | 1945 |
| Meteorological Element | Figure of the Month | Departure from Normal* |
|---|---|---|
| Mean Daily Maximum Air Temperature | 22.4 degrees C | 2.0 degrees above normal |
| Mean Air Temperature | 20.2 degrees C | 2.0 degrees above normal |
| Mean Daily Minimum Air Temperature | 18.4 degrees C | 2.2 degrees above normal |
| Mean Dew Point Temperature | 14.4 degrees C | 2.0 degrees above normal |
| Mean Relative Humidity | 70 % | normal |
| Mean Cloud Amount | 58 % | 1 % above normal |
| Total Rainfall | 6.5 mm | 22.3 mm below normal |
| Number of hours of Reduced VisibilityΔ | 12 hours | 158.1 hours below normal§ |
| Total Bright Sunshine Duration | 166.0 hours | 4.4 hours above normal |
| Mean Daily Global Solar Radiation | 11.86 Megajoule / square metre | 0.95 Megajoule above normal |
| Total Evaporation | 76.5 mm | 4.4 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 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 December 2025