2012 to 2021 is the warmest decade on record.
Singapore, 28 January 2022 – The year 2021 saw significantly wetter-than-average conditions and is Singapore’s second wettest year since 1980. The annual total rainfall at the Changi climate station in 2021 was 33 per cent higher than the long-term average. La Niña conditions present during much of 2021 contributed to higher-than-normal rainfall in the year. The wetter conditions helped to moderate Singapore’s overall temperature in 2021. Nonetheless, the period 2012 to 2021 is Singapore’s warmest decade on record.
2 These findings have been shared in the 2021 Climate and Weather: The Year in Review report, released today by the National Environment Agency’s Meteorological Service Singapore (MSS). The review summarises the main climatic features and notable weather events that affected Singapore in 2021 and is a prelude to the comprehensive Annual Climate Assessment Report, which will be released in conjunction with World Meteorological Day in March 2022. The review is available on the MSS website at www.weather.gov.sg (please refer to the Annex for an infographic on Singapore’s Climate in 2021).
Second Wettest Year Since 1980
3 The annual total rainfall in 2021 was well above average, resulting in the second wettest year since 1980, both at the Changi climate station and based on the islandwide average. The annual total rainfall recorded was 2809.6 mm at the Changi climate station and 3167.7 mm when averaged across islandwide stations with long-term records, which were 33 per cent and 25 per cent above their respective long-term annual averages of 2113.3 mm and 2534.4 mm.
4 Most months in 2021 experienced above-average rainfall. Based on the islandwide average, almost all of these wetter months also ranked within the top 10 wettest for the respective months over the past 40 years. Notably, at the Changi climate station, significantly above-average rainfall was recorded in January with a total rainfall of 692.8 mm, the highest in the past 100 years for the month of January.
5 The last 10 years from 2012 to 2021 is the warmest decade on record. The mean temperature from 2012 to 2021 was 27.97 degrees Celsius, 0.02 degrees Celsius higher than the previous record from 2010 to 2019 (27.95 degrees Celsius). The annual mean temperature in 2021 was 27.9 degrees Celsius, which is 0.1 degree Celsius above the long-term average of 27.8 degrees Celsius. This ranks 2021 as Singapore’s joint 10th warmest year on record (along with 2018, 2014, 2009, and 2004).
6 Singapore’s annual temperature trends in 2021 are similar to the global trends reported in the latest State of the Global Climate 2021 from the World Meteorological Organization. At a global level, with temporary cooling from La Niña conditions early in the year, 2021 is expected to be between the fifth and seventh warmest year on record.
Pacific and Indian Ocean Influences
7 La Niña conditions prevailed during the first quarter of 2021, returning to neutral El Niño – Southern Oscillation (ENSO) conditions in the second quarter. After approximately four months of neutral conditions, La Niña conditions re-emerged towards the end of the third quarter. Along with La Niña conditions, a negative Indian Ocean Dipole (IOD) was also established by the third quarter of 2021. The strength of the negative IOD fluctuated considerably during the second half of the year and returned to neutral by the end of 2021. La Niña conditions and negative IOD events typically result in wetter-than-average conditions over Singapore and the nearby region, particularly during the Southwest Monsoon season.
Notable Weather Events in 2021
A Wet Start to the Year
8 Last year began on a very wet note, with the first half of January experiencing exceptionally wet and cool weather due to a Northeast Monsoon surge, which brought continuous widespread rain over Singapore in the first weekend of the year. The highest daily total rainfall of 210.6 mm was recorded at the Changi climate station on 2 January 2021. Another monsoon surge a week later brought windy and rainy weather on 8-13 January 2021. The rain was heaviest on 10 January 2021, again at Changi climate station, which recorded a daily total rainfall of 204.0 mm.
9 The monthly rainfall recorded at the Changi climate station for January 2021 was 692.8mm, with 648.4 mm recorded in the first fortnight alone. This makes January 2021 the second wettest January since rainfall records began in 1869, exceeding the previous second highest value of 634.5 mm recorded in 1918.
A Very Dry and Windy February
10 The record high rainfall in January 2021 was followed by a very dry February 2021, which saw a highest daily total rainfall of just 46.9 mm at Jurong West on 11 February, while the Changi climate station recorded a mere 1.0 mm for the entire month. February 2021 was the second driest February on record after February 2014 (0.2 mm).
11 February 2021 was also a very windy month, with the Changi climate station recording an average daily wind speed of 13.1 km/h. As a result, February 2021 was the second windiest February since continuous wind records commenced in 1984, behind the 13.7 km/h recorded in February 2014.
Unseasonably Wet August
12 August is normally among the drier months of the year. However, August 2021 saw well-above average rainfall islandwide, with the Changi climate station recording nearly twice its long-term monthly average. There were two days with exceptionally heavy rain that led to flash floods in some areas. On 20 August and 24 August 2021, several spells of moderate to heavy thundery showers fell over the island in the pre-dawn hours and morning. A remarkable daily total rainfall of 247.2 mm was recorded at Mandai station on 24 August 2021, setting a record for the highest daily total rainfall for August, and far surpassing the previous high of 181.8 mm at Changi on 22 August 1983. It was also the wettest day of 2021.
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 According to World Meteorological Organization (WMO) guidelines, the standard climatological normal (derived from meteorological observations) calculated as the average over a 30-year period should be updated every 10 years. As 2021 marked the beginning of a new 30-year climatological period, a new set of climatological normals for Singapore was compiled based on the meteorological data from stations with continuous long-term records from 1991 to 2020.
 2021 is ranked at 21st wettest when compared to the entire climate station record since 1869.
Infographic on Singapore’s Climate in 2021