Sri Lanka is a great tropical island with good weather seasons
If one side of the island has wind and rain, generally the other coast will have good weather. Sometimes there is heavy rain for most of the island – however, this only lasts for a few days normally.
In general, it is best on the South and West coasts in the winter and better weather on the East coast during the summer.
Down South is good all year round, with better sea and surfing conditions in the winter – November through to April.
Upcountry and the Highlands can be cooler throughout the year so take a light waterproof jacket and maybe an umbrella especially in the Winter!
Due to the location of Sri Lanka, within the tropics between 5° 55′ to 9° 51′ North latitude and between 79° 42′ to 81° 53′ East longitude, the climate of the island is lovely and tropical.
The central part of the southern half of the island is mountainous with heights more than 2.5 Km.
The core regions of the central highlands contain many complex topographical features such as ridges, peaks, plateaus, basins, valleys and escarpments.
The remainder of the island is practically flat except for several small hills that rise abruptly in the lowlands.
These topographical features strongly affect the spatial patterns of winds, seasonal rainfall, temperature, relative humidity and other climatic elements, particularly during the monsoon season, when there is always good weather on one of the coasts.
Sri Lanka Winds and Rainfall
The rainfall pattern is influenced by the monsoon winds of the Indian Ocean and Bay of Bengal and is marked by four seasons. This consists of two main seasons and two interseason change periods.
The first main season is in the summer, from mid-May to October, when winds originate in the southwest, bringing moisture from the Indian Ocean. When these winds encounter the slopes of the Central Highlands, they unload heavy rains on the mountain slopes and the southwestern sector of the island. Some of the windward slopes receive up to 250 centimeters of rain per month, but the leeward slopes in the east and northeast receive little rain.
The next interseason change period is autumn and occurs in October and November, the inter-monsoonal months. During this season, periodic squalls occur and sometimes tropical cyclones bring overcast skies and rains to the southwest, northeast, and eastern parts of the island. Although this is warm rain and quite pleasant.
The second main season is the winter season, December to March, monsoon winds come from the northeast, bringing moisture from the Bay of Bengal. The northeastern slopes of the mountains may be inundated with up to 125 centimeters of rain during these months.
The other interseason change period spring occurs from Mid March until mid-May, with light, variable winds, and evening thundershowers.
Humidity is typically higher in the southwest and mountainous areas and depends on the seasonal patterns of rainfall.
At Colombo, for example, daytime humidity stays above 70 percent all year, rising to almost 90 percent during the monsoon season in June.
Anuradhapura experiences a daytime low of 60 percent during the inter-monsoonal month of March, but a high of 79 percent during the November and December rains.
In the highlands, Kandy’s daytime humidity usually ranges between 70 and 79 percent.
Overall rainfall in Sri Lanka has multiple origins. Monsoonal, Convectional and expressional rain accounts for a major share of the annual rainfall.
The mean annual rainfall varies from under 900mm in the driest parts (southeastern and northwestern) to over 5000mm in the wettest parts (western slopes of the central highlands).
Regional differences observed in air temperature over Sri Lanka are mainly due to altitude, rather than to latitude.
The mean monthly temperatures differ slightly depending on the seasonal movement of the sun, with some modified influence caused by rainfall.
The mean annual temperature in Sri Lanka manifests largely homogeneous temperatures in the low lands and rapidly decreasing temperatures in the highlands.
In the lowlands, up to an altitude of 100 m to 150 m, the mean annual temperature varies between 26.5 °C to 28.5 °C, with an annual temperature of 27.5 °C.
In the highlands, the temperature falls quickly as the altitude increases. The mean annual temperature of Nuwara Eliya, at 1800 m sea level, is 15.9 °C.
The coldest month with respect to mean monthly temperature is generally January, and the warmest months are April and August.
The mean annual temperature varies from 27°C in the coastal lowlands to 16°C at Nuwara Eliya, in the central highlands (1900m above mean sea level).
This relatively unique feature manifesting as sunny beaches to rainforests makes this tropical island a great tourist experience.
The Climate of Sri Lanka is dominated by the above mentioned topographical features of the country and the Southwest and Northeast monsoons regional-scale wind regimes.
The Climate experienced during 12 months period in Sri Lanka can be characterized into 4 climate seasons as follows.
Spring – First Inter-monsoon Season
(Mid March – April)
Good for Down South and Upcountry
Warm and uncomfortable conditions, with thunderstorm-type rain, particularly during the afternoon or evening, are the typical weather conditions during this season. The distribution of rainfall during this period shows that the entire South-western sector at the hill country receiving 250 mm of rainfall, with localised area on the South-western slops experiencing rainfall in excess of 700 mm (Keragala 771 mm). Over most parts of the island, the amount of rainfall various between 100 and 250 mm, the notable exception being the Northern Jaffna Peninsula (Jaffna- 78 mm, Elephant pass- 83 mm).
Summer – Southwest -Monsoon Season
(May – September)
Good for East Coast & Upcountry
Windy weather during this monsoon eases off the warmth that prevailed during the 1st Inter monsoon season. Southwest monsoon rains are experienced at any times of the day and night, sometimes intermittently mainly in the Southwestern part of the country.
Amount of rainfall during this season varies from about 100 mm to over 3000 mm. The highest rainfall received in the mid-elevations of the western slops (Ginigathhena- 3267 mm, Watawala- 3252 mm, Norton- 3121 mm).
Rainfall decreases rapidly from these maximum regions towards the higher elevation, an in Nuwara Eliya drops to 853 mm.
The variation towards the Southwestern coastal area is less rapid, with the Southwestern coastal belt experiencing between 1000 mm to 1600 mm of rain during this 5-month long period.
Autumn – Second Inter-monsoon Season
Good for Upcountry
The thunderstorm-type of rain, particularly during the afternoon or evening, is the typical climate during this season. But unlike in the Intermonsoon season, the influence of weather system like depression and cyclones in the Bay of Bengal is common during the second Intermonsoon season.
The whole country experiences strong winds with wide spread rain, sometwidespreadg to floods and landslides.
Almost the entire island receives in excess of 400 mm of rain during this season, with the Southwestern slopes receiving higher rainfall in the range 750mm to 1200 mm (Weweltalawa Estate in Yatiyantota recording 1219 mm)
Winter – Northeast -Monsoon Season
(December – Mid March )
The dry and cold wind blowing from the Indian land-mass will establish a comparatively cool, but dry weather over many parts making the surrounding pleasant and comfortable weather except for some rather cold morning hours.
Cloud-free skies provide days full of sunshine and pleasant and cool night.
During this period, the highest rainfall figures are recorded in the North, Eastern slopes of the hill country and the Eastern slopes of the Knuckles/Rangala range.
The maximum rainfall is experience at Kobonella estate (1281 mm), and the minimum is in the Western coastal area around Puttalam (Chilaw- 177 mm) during this period.