Sri Lanka's position between 5 and 10 north latitude endows
the country with a warm climate, moderated by ocean winds and
considerable moisture. The mean temperature ranges from a low of
15.8° C in Nuwara Eliya in the Central Highlands (where frost
occur for several days in the winter) to a high of 29° C in
Trincomalee on the northeast coast (where temperatures may reach
37° C). The average yearly temperature for the country as a
ranges from 26° C to 28° C. Day and night temperatures may
4 to 7 . January is the coolest month, causing people,
especially those in the highlands, to wear coats and sweaters.
May, the hottest period, precedes the summer monsoon rains.
The rainfall pattern is influenced by the monsoon winds of
the Indian Ocean and Bay of Bengal and is marked by four seasons.
The first is 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 second season occurs in
October and November, the intermonsoonal 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. During the third 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. Another intermonsoonal period occurs from 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 intermonsoonal 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.
Data as of October 1988