The Climate of Sri Lanka...

Since Sri Lanka is located near the equator, it has high temperatures and high rainfall distribution throughout the year. There is a uniform temperature over the year. Sri Lanka's annual temperature is about 26.8 ⁰C. But according to the altitude, temperature differences can observe locally. There are three primary sources of rainfall in Sri Lanka.

  01. Inter-monsoonal (Convectional)
  02. Monsoonal
  03. Cyclonic

Inter-monsoonal rainfall received at two different periods. The first inter-monsoonal rainfall received in March-April, and the second is obtained in September-October.
Monsoonal rainfall also received at two periods. The first monsoonal rainfall or the 'south-west monsoon' obtained in May-September. The second rainfall or the 'north-east monsoon' obtained in October-January.
Cyclones are unpredictable. They can occur at any time of the year, but more prevalent during November-December.
Based on the temperature and the rainfall, five climatic zones are defined in Sri Lanka.

01. Low country wet zone
02. Low country dry zone
03. Hill country wet zone
04. Hill country dry zone
05. Semi-arid zone

Let's take a look at these climate zones in more detail.

Low country wet zone

Here the annual rainfall is more than 2000 mm, and the average yearly temperature is more than 27 ⁰C. The primary rainfall source is the south-west monsoon and inter-monsoon.

Low country dry zone

The annual rainfall is about 1250 mm - 2000 mm, and the yearly average temperature is more than 27 ⁰C. North-east monsoon and inter-monsoons bring the rain. But during the period of May - September, drought season of about two months can be seen in this zone.

Hill country wet zone

The annual rainfall is about 3000 mm. But some areas, like Watawala, Maliboda, received more than 5000 mm rainfall annually. The western half of the central hill country is under this zone. 

Hill country dry zone

The eastern part of the central hill country is under this zone. About 1750 mm - 2000 mm rainfall received annually. 

Semi-arid zone

The average annual rainfall is below 1250 mm, and the average temperature is over 27 ⁰C. Here, rain is minimal. It is about 3-4 months. Most of the precipitation received from the inter-monsoons.