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The Weather of January 2025 - A dry and sunny January

4 February 2025

With the dominance of dry northeast monsoon over southern China for most of the time in the month, January 2025 was marked by dry and sunny weather in Hong Kong. The monthly total sunshine duration amounted to 222.3 hours, about 52 percent above the normal of 145.8 hours. 4.2 millimetres of rainfall were recorded in the month, only about 13 percent of the normal of 33.2 millimetres in the month. The monthly mean relative humidity of 59 percent was 15 percent below the normal of 74 percent and the third lowest on record for January. The month was also slightly warmer than usual with the mean temperature of 17.1 degrees, 0.6 degrees above the normal of 16.5 degrees.

Affected by an easterly airstream, the weather of Hong Kong was mainly cloudy on the first two days of the month, with one or two light rain patches on 1 January. Under the influence of the northeast monsoon, it was generally fine on 3 – 9 January apart from a few light rain patches on the night of 4 January and on the morning of 5 January. 

With the arrival of an intense winter monsoon on the night of 9 January, the weather was cold on the mornings of the following three days. It was very dry with the relative humidity over the territory staying at 30 percent or below during the day on 12 January. The daily minimum relative humidity of 9 percent at Chek Lap Kok was the second lowest on record for January since the station was established in June 1997. As the monsoon was replaced by an easterly airstream, the weather turned milder gradually on 13 – 15 January. The temperatures at the Observatory rose to a maximum of 22.3 degrees on the afternoon of 15 January, the highest of the month. 

Under the influence of a dry northeast monsoon, it was generally fine with cool mornings on 16 – 20 January. Affected by a fresh to strong easterly airstream and a band of clouds covering the coast of Guangdong, local weather became cloudier with a few rain patches in the following three days. With the band of clouds thinning out, it was generally fine on 24 – 25 January.

A cold front moved across the coast of southern China on the morning of 26 January. Locally, it was mainly cloudy with one or two rain patches on that day. With the strengthening of the northerlies, the weather of Hong Kong became cold progressively that night. Under the influence of the associated intense winter monsoon, it turned generally fine and very dry with cold mornings on 27 – 28 January. The temperatures at the Observatory dropped to a minimum of 10.6 degrees on the morning of 27 January, the lowest of the month. The monsoon was gradually replaced by a fresh to strong easterly airstream on 29 January. While it was cloudy at first, the weather turned fine and very dry during the day. With a band of clouds setting in over the coast of Guangdong, the weather turned cloudy on the night of 30 January and there were one or two rain patches on the last day of the month.

There was no tropical cyclone over the South China Sea and the western North Pacific in January 2025.

Details of issuance and cancellation of various warnings/signals in the month are summarised in Tables 1.1 to 1.4.  Monthly meteorological figures and departures from normal for January are tabulated in Table 2.

 

Warnings and Signals issued in January 2025

Table 1.1   Strong Monsoon Signal
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
26 / 1 1530 27 / 1 1145


Table 1.2   Fire Danger Warnings
Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Red 3 / 1 0600 3 / 1 2315
Yellow 4 / 1 0600 4 / 1 2130
Red 5 / 1 0600 5 / 1 1945
Red 6 / 1 0600 6 / 1 2330
Red 9 / 1 0600 13 / 1 2345
Red 15 / 1 0600 18 / 1 2330
Red 19 / 1 0600 19 / 1 2245
Red 20 / 1 0600 20 / 1 2310
Red 21 / 1 0600 21 / 1 1645
Red 27 / 1 0600 30 / 1 0600
Yellow 30 / 1 0600 30 / 1 2145
Yellow 31 / 1 0600 31 / 1 1800


Table 1.3   Frost Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
10 / 1 1630 11 / 1 0745
11 / 1 1630 12 / 1 0745


Table 1.4   Cold Weather Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
9 / 1 1620 13 / 1 1015
26 / 1 1100 29 / 1 0900


Table 2   Figures and Departures from Normal - January 2025
Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 19.8 degrees C 1.1 degrees above normal
Mean Air Temperature 17.1 degrees C 0.6 degrees above normal
Mean Daily Minimum Air Temperature 15.0 degrees C 0.4 degrees above normal
Mean Dew Point Temperature 8.5 degrees C 3.2 degrees below normal
Mean Relative Humidity 59 % 15 % below normal
Mean Cloud Amount 44 % 18 % below normal
Total Rainfall 4.2 mm 29.0 mm below normal
Number of hours of Reduced VisibilityΔ 2 hours 190.3 hours below normal§
Total Bright Sunshine Duration 222.3 hours 76.5 hours above normal
Mean Daily Global Solar Radiation 14.82 Megajoule / square metre 4.27 Megajoule above normal
Total Evaporation 101.3 mm 32.2 mm above 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 2024

Daily values of selected meteorological elements for Hong Kong for January 2025

The percentile map of mean temperature of January 2025

  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 January 2025