Blogs
Climate Bulletin for Sri Lanka (Week of 19 September – 26 September 2025)
Highlights
Rainfall Prediction: Sri Lanka is reaching the end of its dry season. During the next week, rainfall is expected to be 35–45 mm/week in Central and Eastern provinces; 25-35 mm/week in Northern, North-Central, North-Western, Western, Sabaragamuwa, Southern districts.
Monitored Rainfall:The 30 day cumulative rainfall till 15th September shows that rainfall totaled about 37mm whereas the expected rainfall was 72mm. During 09-16 September, Sri Lanka recorded an average rainfall of 1.8 mm/day, compared to 3.6 mm/day received in the hydro-catchment areas.
Monitored and Predicted Wind: From 08-14 September, winds at 1.5 km height was mostly from the West at speeds ranged 3-8 m/s. From 17-18 September, wind speeds are predicted to range between 2-15 m/s coming from the North-West.
Monitored Sea and Land Temperature: Average maximum land surface temperature was 32.06C during 09 -16 September. The Eastern Plains were the warmest, followed by Northern and Southern Plains. From 08–14 September, the sea surface temperature was warmer around Northern, Southern, Western and Eastern coasts, ranging between 1 °C and 1.5 °C above average.
Interpretation
Monitoring
Rainfall: Average Rainfall in the regions for the previous week of (09 September-16 September) = 1.8 mm/day. Maximum Daily Rainfall: 33.1 mm & Minimum Daily Rainfall: 0.0 mm.
Wind: Westerly winds prevailed over the sea area and around the island last week, with wind speeds ranging between 3-8 m/s from 08-14 September.
Temperatures: From August 7 to September 13, Sri Lanka experienced above-normal temperature anomalies, except in Northern, North-Central (some areas), North-Western (some areas), and part of the Eastern province.
Prediction
Rainfall: During the next week, rainfall is expected to be 35–45 mm/week in Central and Eastern provinces; 25-35 mm/week in Northern, North-Central, North-Western, Western, Sabaragamuwa, Southern districts.
Temperatures: The temperature will remain above normal in some parts of the Northern, North-Central, Uva, Southern, Eastern and North-Western provinces and in Matale with maximum temperatures reaching between 34°C and 37°C of Sri Lanka from 18 September – 02 October.
Teleconnections: The MJO will remain in a near-neutral phase regarding rainfall from September 16–30.
Seasonal Precipitation: The precipitation forecast for the October-November-December 2025 season shows near-neutral tendency for 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 |
