Singapore’s climate is for the most part similar to its neighboring countries which are also located near the equator. Common weather characteristics that can be observed with regard to the climates in the area include high temperature and high levels of rain. Because also of their location, weather patterns experienced by the people who live in the countries in this region are almost constant with no dramatic changes felt throughout the year. Because of these factors, the chances of predicting the weather can prove to very precise and concise in the country.
It is interesting to note that there are some slight weather discrepancies within Singapore. The western side of the country tends to be slightly wetter and has slightly lower temperatures than the eastern side. There have also been reported incidents where rain is falling heavily on one side of the country with the sun shining brightly on the other.
General Weather Patterns
Owing to its location near the equator, Singapore’s climate is characterized by constant temperature, high levels of humidity, and abundant rainfall. Singapore’s climate is classified as a tropical rainforest. It has no true dry or wet seasons as it experiences high temperature and heavy rains constantly and almost uniformly throughout the year. Daily average temperatures range from 26oCto 28oC throughout the year. Rainfall averages are lowest in July at 160mm and highest at December at 287.4mm.
Singapore also experiences high levels of humidity with an average relative humidity of around 85% constantly throughout the year. However, this can go up to 100% during long periods of heavy rains. Relative humidity varies more during the day where it can be as high as 90% during mornings, and decreasing to about 60% during afternoons.
Although it has no characterized dry and wet seasons, Singapore has two distinct monsoon seasons: the Northeast Monsoon, from December to March, and the Southwest Monsoon, from June to September. During these two seasons, moderate to heavy rains are to be expected along with gusts of strong winds.
In between these two monsoon seasons are two inter-monsoon periods, which are generally characterized by hotter temperatures and the prevalence of thunderstorms, especially in the afternoon and the early evening.
Winds in Singapore are heavily influenced by the monsoon flow and are usually from the northeast and the south. Directions are mostly northerly during the Northeast Monsoon and southerly in the Southwest Monsoon. It is observed that winds are strongest during the Northeast Monsoon as compared to other times in the year especially when compared to the inter-monsoon periods in between the two monsoon seasons where winds are reported to be lighter.
Surface wind speeds are generally pleasant at 2.5m/s. During heavy rains and thunderstorms, however, surface wind speeds have been measured to reach average speeds of 10m/s. On a daily average, winds can be stronger during the day and become lighter as night falls.
Because of Singapore’s proximity to the equatorial line, it generally has longer days and longer periods of exposure to the sun owing to the virtually constant distance of the country to the sun throughout the year. The number of hours of sunshine in the country can vary depending on a number of factors which include the presence of clouds and the level of rainfall on a particular day. On average, sunshine duration during rainy days range from about four to five hours. They can, however, go up to as high as eight to nine hours in the drier days.
Visibility and Cloud Cover
The most common low cloud types in Singapore are the cumulus, stratocumulus, and cumulonimbus clouds. Cumulus clouds usually develop during the midday with tops reaching 2.5 – 3.5km above the ground. These cumulus clouds, in the right conditions, can develop into cumulonimbus clouds in the afternoon with tops up to 9 – 12km high. These clouds usually dissipate at dusk and diffuse during the night.
During monsoon surges, layers of rain clouds are present producing heavy amounts of rain across wide areas. Low stratus clouds are also commonly observed during this time. Other low-lying rain clouds are also prevalent during rainy days.
On average, visibility in Singapore is good. Visibility, however, can be greatly affected when there are heavy rains and thunderstorms, especially during the evening. Several naturally-occurring weather conditions can also arise which can significantly hamper visibility. One of the more common ones is the presence of mist. Mist usually forms in the wee hours of the morning and can cause visibility problems during this time. Usually, however, mist begins to dissipate once the sun shines and visibility goes back to normally clear levels.
Visibility also becomes very poor when there is haze. There have been reports where the visibility reached levels below 1km in cases of severe haze.
Haze and Other Environmental Concerns
Haze is an atmospheric occurrence where the clarity of the sky and the general visibility level is obscured by dust, smoke, and other dry particles present in the atmosphere. Sources of particles which can cause haze are mostly and primarily from human activities like farming, vehicles and traffic, general industry, and assisted forest fires and wildfires.
Haze in Singapore has been mostly caused by forest fires from neighboring countries. The effect can be amplified when accompanied by dry weather, low amounts of rain, and unfavorable wind conditions. Winds can oftentimes carry haze from other regions, and even other countries, to Singapore. In 2013, the winds carried haze caused by large-scale fires from Indonesia and as far as Borneo to Singapore. This caused severe levels of haze in Singapore which reached the point that the government had to step in and cancel outdoor activities in school and work, and distribute masks.
The government agency which handles haze-related policies and actions is the National Environment Agency. The NEA is directly under the Ministry of the Environment and Water Resources. It releases timely general weather information bulletins to the public regarding the level of haze and it also issues health advisories relating to haze when the situation calls for it.