Blogs
Climate Bulletin for Sri Lanka (Week of 15 – 22 August 2025)
Highlights
Rainfall Prediction: For 12-18 August, rainfall/week is expected as 25-35 in the Matale, Kandy districts 5-25 in the Kegalle, Nuwara Eliya, Badulla districts 0-5 in the Northern, Eastern, North-Central, Western, North-Western, Southern provinces and Moneragala, Ratnapura districts
Monitored Rainfall: During 4-11 August, Sri Lanka received an average rainfall of 2 mm/day, while in the hydro catchments, the average rainfall was 2.3 mm/day. Jaffna recorded the highest daily rainfall on 10th August, reaching 58.4 mm.
Monitored and Predicted Wind: From 04-10 August, winds at 1.5 km was mostly from the North-West at speeds ranging between 5-15 m/s. From 13-19 August, wind speeds are predicted to be ranging between 4-15 m/s and expected to come from the North-West.
Monitored Sea and Land Temperature: Average maximum land surface temperature was 31.6 °C during 4-11 August. The Eastern Plains were the warmest, followed by Southern and Northern Plains. From 4-10 August, the sea surface temperature is near-neutral around the Southern and Western coast while it is warmer around the Northern and South-Eastern coasts, ranging between 1.0 °C to 1.5 °C above-average levels.
Interpretation
Monitoring
Rainfall: Average Rainfall in the regions for the previous week of (4-11 August) = 1.8 mm/day. Maximum Daily Rainfall: 58.4 mm & Minimum Daily Rainfall: 0.0 mm.
Wind: North-Westerly winds prevailed over the sea area and around the island last week, with wind speeds ranging between 5-15 m/s from 4-10 August.
Temperatures: Temperature anomalies were near-neutral in Sri Lanka except fro some parts in Northern, Eastern and North-Eastern provinces from July 3 to 9 August .
Prediction
Rainfall: During the next week, 25-35 mm/week rainfall is expected for Matale, Kandy districts, while 5-25 mm/week rainfall is predicted for Badulla, Kegalle, Nuwara Eliya districts, while 0-5 mm/week rainfall is predicted for the Northern, Eastern, North-Central, Western, North-Western, Southern provinces and Moneragala, Ratnapura districts.
Temperatures: The temperature will remain above normal in Mullaitivu, Vavuniya, Kilinochchi, Anuradhapura, Polonnaruwa, Trincomalee, Batticaloa, Ampara, Moneragala, Badulla, Hambantota districts with maximum temperatures reaching between 35°C and 39°C of Sri Lanka from 14-27 August.
Teleconnections: The MJO will slightly enhance the rainfall from 12 to 21 August, near-neutral from 22 to 26 August.
Seasonal Precipitation: The precipitation forecast for the August-September-October 2025 season shows a 40% of tendancy below normal in the Southern half of Sri Lanka.
Terminology for Rainfall Ranges
| Terminology | Rainfall (mm/week) |
| Light Showers | Less than 12.5 mm |
| Light to Moderate | Between 12.5 mm and 25 mm |
| Moderate | Between 25 mm and 50 mm |
| Fairly Heavy | Between 50 mm and 100 mm |
| Heavy | Between 100 mm and 150 mm |
| Very Heavy | More than 150 mm |
