Blogs
Climate Bulletin for Sri Lanka (Week of 22 – 29 August 2025)
Highlights
Rainfall Prediction: For 19-25 August, rainfall/week is expected as 25-35 in the Kandy districts 5-25 in the Matale, 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 11-18 August, Sri Lanka received an average rainfall of 2 mm/day, while in the hydro catchments, the average rainfall was 7.4 mm/day. Ratnapura recorded the highest daily rainfall on 11th August, reaching 28 mm.
Monitored and Predicted Wind: From 11-17 August, winds at 1.5 km was mostly from the North-West at speeds ranging between 10-15 m/s. From 20-26 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 31.3 °C during 11-18 August. The Eastern Plains were the warmest, followed by Southern and Northern Plains. From 11-17 August, the sea surface temperature is near-neutral around the Southern and Western coasts while it is warmer around the Northern coast, 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 (11-18 August) = 1.7 mm/day. Maximum Daily Rainfall: 27.9 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 10-15 m/s from 11-17 August.
Temperatures: Temperature anomalies were near-neutral in Sri Lanka from July 10 to 16 August.
Prediction
Rainfall: During the next week, 25-35 mm/week rainfall is expected for Kandy districts, while 5-25 mm/week rainfall is predicted for Matale, 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, Kurunegala, Puttlam, Matale districts with maximum temperatures reaching between 35°C and 39°C of Sri Lanka from 21 August – 03 September.
Teleconnections: The MJO will slightly enhance the rainfall from 19 August to 03 September.
Seasonal Precipitation: The precipitation forecast for the September-October-November 2025 season shows a 45% of tendancy below normal in the Northern province of Sri Lanka and 50% of tendancy below normal in the rest of the provinces.
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 |
