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The Weather of November 2020

2 December 2020

With the northeast monsoon over southern China generally weaker than normal for most of the time in the month, November 2020 was much warmer than usual in Hong Kong. The monthly mean maximum temperature was 26.4 degrees, 2.3 degrees above the normal figure and the highest on record for November. The monthly mean temperature of 23.5 degrees and mean minimum temperature of 21.7 degrees were respectively 1.7 degrees and 1.9 degrees above their corresponding normal figures and both were the second highest on record for November. Moreover, the autumn mean temperature in Hong Kong for the period from September to November 2020 was 25.8 degrees, 0.8 degrees above the normal figure and one of the fourth warmest autumns on record. The month was also drier than usual with a total rainfall of 5.1 millimetres, about 14 percent of the normal figure of 37.6 millimetres. The accumulated rainfall this year up to November was 2393.5 millimetres, slightly more than the normal figure of 2371.7 millimetres for the same period.

Dominated by a dry northeast monsoon, apart from cloudy interludes on 3 and 8 November and a few light rain patches on 3 – 4 November, the weather of Hong Kong was generally fine and dry during the day on the first eight days of the month. With plenty of sunshine, the maximum temperature at the Observatory rose to 30.2 degrees on 7 November, the highest of the month and also the hottest Winter Commences on record. Meanwhile, tropical cyclone Etau moved across the southern part of the South China Sea on 8 - 10 November. Affected by the outer cloud band associated with Etau, local weather turned cloudy with a few light rain patches on the afternoon of 9 November and remained generally cloudy the next day.

Under the influence of the dry northeast monsoon, it was generally fine and dry during the day with slightly cooler mornings on 11 – 12 November. Meanwhile, tropical cyclone Vamco moved across the central part of the South China Sea on 12 - 15 November. Affected by the outer cloud band associated with Vamco, local weather became mainly cloudy with a few light rain patches on 13 – 15 November. Dominated by the anticyclone aloft, sunny weather returned on 16 – 17 November.

Affected by an easterly airstream, local weather became warmer with a few mist and light rain patches on 18 - 19 November. Under light wind conditions, it was cloudy with coastal fog on the morning of 20 November. The visibility at Waglan Island once fell below 200 metres. With the cloud layer thinning out, the weather became sunny and hot in that afternoon. A surge of the northeast monsoon reached the coast of Guangdong on the morning of 21 November. Locally, there was coastal fog at first. The weather turned mainly cloudy and cooler with a few rain patches on that day. While there were a few light rain patches on the morning of 22 November, the weather gradually turned fine during the day.

Under the influence of a replenishment of the northeast monsoon, it was cooler, cloudy with a few light rain patches on 23 November. The clouds gradually thinned out and local weather became generally fine and dry on 24 – 26 November. Affected by another replenishments of the northeast monsoon, the weather became windier with cooler mornings towards the end of the month. The temperature at the Observatory dropped to a minimum of 16.4 degrees on the morning of 30 November, the lowest of the month.

Four tropical cyclones occurred over the South China Sea and the western North Pacific in November 2020.

Details of issuance and cancellation of various warnings/signals in the month are summarized in Tables 1.1 to 1.2.  Monthly meteorological figures and departures from normal for November are tabulated in Table 2.

Warnings and Signals issued in November 2020

Table 1.1   Strong Monsoon Signal
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
23 / 11 0445 24 / 11 0515


Table 1.2   Fire Danger Warnings
Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Yellow 1 / 11 0600 1 / 11 1900
Red 7 / 11 0600 8 / 11 2240
Red 9 / 11 1100 9 / 11 1800
Red 10 / 11 1100 10 / 11 2130
Red 11 / 11 0800 11 / 11 1930
Red 12 / 11 1130 12 / 11 1900
Yellow 15 / 11 1000 15 / 11 1800
Yellow 22 / 11 0600 22 / 11 1800
Red 28 / 11 0600 28 / 11 1800
Yellow 29 / 11 0600 29 / 11 2300


Table 2   Figures and Departures from Normal - November 2020
Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 26.4 degrees C 2.3 degrees above normal
Mean Air Temperature 23.5 degrees C 1.7 degrees above normal
Mean Daily Minimum Air Temperature 21.7 degrees C 1.9 degrees above normal
Mean Dew Point Temperature 17.8 degrees C 1.8 degrees above normal
Mean Relative Humidity 71 % normal
Mean Cloud Amount 60 % 6 % above normal
Total Rainfall 5.1 mm 32.5 mm below normal
Number of hours of Reduced VisibilityΔ 8 hours 109.2 hours below normal§
Total Bright Sunshine Duration 192.6 hours 12.5 hours above normal
Mean Daily Global Solar Radiation 13.81 Megajoule / square metre 1.53 Megajoule above normal
Total Evaporation 98.0 mm 1.5 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 1981 - 2010 climatological normal, except for number of hours of reduced visibility

  §   Departure from mean value between 1997 and 2019
daily values of selected meteorological elements for HK for November 2020

The percentile map of mean temperature of November 2020

  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 1981 to 2010


Extract of Meteorological Observations in Hong Kong for November 2020