Sri Lanka - Climate
Sri Lanka is in a tropical rain forest climate, with some variety in different regions. This variety is relative; areas described as “dry” are still much more humid than Arizona. Living things of all kinds thrive, regardless of the housekeeper’s efforts to discourage some of them. Geckos, small lizards with little suckers on their feet, live on the walls and ceilings of many homes and offices. They make a chirping sound, and live on mosquitoes and other small flying insects, and do not bite. Their tails are sometimes bitten off by birds or cats, but they grow back. Ants, cockroaches, silverfish, beetles, worms, giant black scorpions, termites, flying ants, gnats, spiders, leeches, and other creatures do their best to share the benefits of roof, walls, and clean water. Few of these creatures will harm you, but some are alarming on first acquaintance. Devout Buddhists and Hindus will not kill them — they will tenderly scoop them up and toss them outside.
It takes about six weeks to get acclimated. Fluid intake should be increased to make up for the loss due to evaporation of perspiration. It is not unusual to lose 2-3 quarts of water by perspiration while engaged in outdoor sports and other heavy physical activities. Heat and humidity cause foods to spoil rapidly. Humidity, plus heat, promote the growth of skin fungus and bacteria.
Sri Lanka occasionally experiences heavy rain fall due to depressions around the island. Heavy rainfall has resulted in flooding in low lying urban areas and near rivers. Landslides have occurred during and after heavy rains in Colombo, as well as Central, Western, Sabaragamuwa, and other Provinces depending upon prevailing weather conditions.
Seasons
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 may 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 whole ranges from 26°C to 28°C. Day and night temperatures may vary by 4° to 7°. January is the coolest month, causing people, especially those in the highlands, to wear coats and sweaters. In Nuwera Eliya, and the surrounding areas in the central “hill country “, it is wet and cold for six to eight months of the year, the nights being particularly chilly, sometimes frosty. 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 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.
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.
Ecological Zones
The pattern of life in Sri Lanka depends directly on the availability of rainwater. The mountains and the southwestern part of the country, known as the "wet zone," receive ample rainfall (an annual average of 250 centimeters). Most of the southeast, east, and northern parts of the country comprise the "dry zone," which receives between 120 and 190 centimeters of rain annually. Much of the rain in these areas falls from October to January; during the rest of the year there is very little precipitation, and all living creatures must conserve precious moisture. The arid northwest and southeast coasts receive the least amount of rain — 60 to 120 centimeters per year — concentrated within the short period of the winter monsoon.
The natural vegetation of the dry zone is adapted to the annual change from flood to drought. The typical ground cover is scrub forest, interspersed with tough bushes and cactuses in the driest areas. Plants grow very fast from November to February when rainfall is heavy, but stop growing during the hot season from March to August. Various adaptations to the dry conditions have developed. To conserve water, trees have thick bark; most have tiny leaves, and some drop their leaves during this season. Also, the topmost branches of the tallest trees often interlace, forming a canopy against the hot sun and a barrier to the dry wind.
When water is absent, the plains of the dry zone are dominated by browns and grays. When water becomes available, either during the wet season or through proximity to rivers and lakes, the vegetation explodes into shades of green with a wide variety of beautiful flowers. Varieties of flowering acacias are well adapted to the arid conditions and flourish on the Jaffna Peninsula. Among the trees of the dry-land forests are some valuable species, such as satinwood, ebony, ironwood, and mahogany.
In the wet zone, the dominant vegetation of the lowlands is a tropical evergreen forest, with tall trees, broad foliage, and a dense undergrowth of vines and creepers. Subtropical evergreen forests resembling those of temperate climates flourish in the higher altitudes. Montane vegetation at the highest altitudes tends to be stunted and windswept.
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