Blogs
Climate Bulletin for Sri Lanka (Week of 29 August – 05 September 2025)
Highlights
Rainfall Prediction: Sri Lanka is reaching the end of its dry season Moderate rainfall of 25–35 mm is expected in the Kandy District during 28 August–03 September, while light rainfall of 5–25 mm rainfall in surrounding districts. Other regions are likely to experience very little rain.
Monitored Rainfall: Rainfall was low last week, compared with the seasonal historical average. During 18-25 August, Sri Lanka received an average rainfall of 1 mm/day, while in the hydro catchments, the average rainfall was 0.6 mm/day.
Monitored and Predicted Wind: August has the highest winds in Sri Lanka generally. From 19-25 August, winds at 1.5 km height was mostly from the North-West at speeds ranged 8-10 m/s. From 28 August-03 September, wind speeds are predicted to increase to a range between 10-15 m/s coming from the North-West.
Monitored Sea and Land Temperature: Average maximum land surface temperature was 32.8 °C during 18-25 August. The Eastern Plains were the warmest, followed by Southern and Northern Plains. From 19-25 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 (18-25 August) = 0.5 mm/day. Maximum Daily Rainfall: 14.9 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 8-10 m/s from 19-25 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 29 August – 12 September.
Teleconnections: The MJO will slightly enhance the rainfall from 26 August to 09 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 |
