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Climate Bulletin for Sri Lanka (Week of 03 October – 10 October 2025)
Highlights
Rainfall Prediction: With Maha season initiating, rainfall will pick up across SL. From 30 Sept – 06 Oct, total rainfall by province is predicted to be 35–45 mm in Central, Sabaragamuwa, Western and North – Western; 25-35 mm in North-Central, Eastern, Southern and Uva; 0-15mm/week in Northern.
Monitored Rainfall:Sri Lanka recorded an average rainfall of 28.0 mm/week. During 23-30 September, rainfall has been above normal, especially on 25th, in the Western Slopes and Western Coasts, driven by the interaction of wind and mountain slopes with the highest totals at Galle (160mm), Ratnapura (147mm) and Ratmalana (82mm).
Monitored and Predicted Wind: Strong Winds continued to come from the South-West. From 22-28 September, winds at 1.5 km height was mostly from the West and North West at speeds of 8-10 m/s From 01-07 October, wind speeds are predicted to range between 1-8 m/s coming from the North-West and West.
Monitored Sea and Land Temperature: Sri Lanka recorded seasonable temperatures across its regions. The Eastern Plains were the warmest, with maximum temperature of 35 °C , compared to 31 °C in the Western Plains. From 22–28 Sept, the sea surface temperature was warmer than average around Northern coasts by 1 – 1.5 °C and the Southern and Eastern coasts by 0.25- 0.5 °C.
Interpretation
Monitoring
Rainfall: Average Rainfall in the regions for the previous week of (23 September-30 September) = 4.0 mm/day. Maximum Daily Rainfall: 95.5 mm & Minimum Daily Rainfall: 0.0 mm.
Wind: Westerly and North Westerly winds prevailed over the sea area and around the island last week, with wind speeds ranging between 8-15 m/s from 22-28 September.
Temperatures:During the period 21–27 September, Sri Lanka experienced near-neutral conditions.
Prediction
Rainfall:From 30 September – 06 October, rainfall is expected to be 35–45 mm/week in Central, Sabaragamuwa, Western and North-Western provinces; 25-35 mm/week in North-Central, Eastern, Southern and Uva provinces; 0-15mm/week in Northern province.
Temperatures: The temperature will remain above normal in some parts of the Northern, North-Central, Uva, Southern, Eastern and Sabaragamuwa provinces and in Monaragala with maximum temperatures reaching between 34°C and 39°C of Sri Lanka from 02- 15 October.
Teleconnections: The MJO remain slightly enhanced for rainfall from 30 September – 4 October, near neutral from 5-9 October and slightly suppressed from 10-14 October.
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 |
