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High Likelihood Of El Nino Conditions In Second Half Of 2023 Will Increase Risk Of Transboundary Haze Affecting Singapore

30 May 2023

Warmer and drier conditions predicted in the coming months 

Singapore, 30 May 2023 – The Meteorological Service Singapore (MSS) is forecasting El Niño [1] conditions to develop in the second half of 2023. A positive Indian Ocean Dipole [2] (IOD) is also predicted to develop during this period. Both climate phenomena are expected to bring warmer and drier conditions to Singapore and the surrounding region from June to October 2023, and this will increase the risk of transboundary haze affecting Singapore and the region.   

High likelihood of El Niño

2          According to MSS, there is a 70-80 per cent chance of an El Niño event occurring this year. There are already signs since earlier this year that support El Niño conditions developing in the next few months. These include the warmer subsurface ocean temperatures observed in the eastern tropical Pacific, typically a precursor to El Niño events.

3          El Niño events tend to have the biggest influence on Singapore’s rainfall during the Southwest Monsoon season from June to September, with rainfall up to 45 per cent below average. During the last strong El Niño event in 2015/2016, Singapore’s total rainfall from June to September 2015 was about 35 per cent below the long-term average.

4          El Niño events also bring warmer temperatures to Singapore, with the warmest temperatures often occurring when El Niño events weaken typically in March to April the year following the start of the event. During the 2015/2016 El Niño event, Singapore’s average temperature over the June-September 2015 period was 28.8 degrees Celsius or 0.6 degree Celsius above its long-term average for that period. For the period from March-April 2016, Singapore average temperature was 29.2 degrees Celsius or 1.2 degrees Celsius above its long-term average for that period. 2016, together with 2019, are Singapore’s hottest years on record.      

5          At this stage, there is no indication of the strength and duration of the El Niño, if it develops. Should a strong El Niño set in, well below average rainfall and warmer temperatures can be expected during the coming Southwest Monsoon season.     

Potential Positive Indian Ocean Dipole (IOD)

6          El Niño is a major, but not the only, driver of the earth’s climate system. The IOD is another climate phenomenon that can influence the weather around the tropical Indian Ocean. Most computer models from global climate centres predict that a positive IOD may develop in the next one to two months. During positive IOD events, sea surface temperatures in the eastern Indian Ocean are cooler, resulting in less cloud formation and below average rainfall in the eastern Indian Ocean and surrounding regions including Sumatra, Peninsular Malaysia and Singapore.

Risk of Transboundary Haze

7          The Southwest Monsoon period between June and September is the usual dry season for Singapore and the surrounding region. With an expected El Niño and positive IOD, the dry season this year could be more intense and prolonged compared to recent years [3], and extend into October.

8          Drier and warmer conditions are conducive to the development of peatland and vegetation fires. Therefore, hotspots could escalate from June 2023 under extended periods of drier weather, particularly in fire prone areas. This will increase the risk of transboundary haze affecting Singapore if fires develop in close proximity and prevailing south-easterly to south-westerly winds blow smoke haze from the fires towards Singapore.

9          MSS will continue to closely monitor the development of El Niño and IOD as well as the regional weather and haze situation, and provide updates when necessary. Updates on haze and the El Niño are available in the MSS website at and

Haze Preparedness

10        In anticipation of the onset of drier weather, the government Inter-Agency Haze Task Force (HTF) has been co-ordinating action plans in preparation for possible haze. Members of the public are also advised to make preparations such as ensuring that they have sufficient N95 face masks and air purifiers in good working condition. More details can be found in NEA's advisories which are available on the NEA website, MyENV app, and the haze microsite. When a haze episode is imminent, NEA will provide haze forecasts through the aforementioned sites. Follow NEA’s Facebook and Twitter (@NEAsg) for the latest updates.

[1] El Niño is a naturally occurring climate pattern associated with changes in both the ocean and atmosphere in the equatorial Pacific Ocean, including an abnormal warming of the surface waters in the eastern equatorial Pacific. Typically lasting 9-12 months and occurring every three to five years, it produces widespread and at times severe changes in the global climate.

[2] The Indian Ocean Dipole (IOD) is similar to the El Niño but occurs in the equatorial Indian Ocean and of shorter duration, typically ending by December-January. The IOD varies between three phases – positive, negative and neutral.

[3] La Niña conditions were present between 2020 and 2023 (with a short break in 2021) which contributed to above normal rainfall for most parts of the southern ASEAN region during the dry seasons of those years.

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