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Climate Bulletin for Sri Lanka (Week of 10 October – 17 October 2025)
Highlights
Rainfall Prediction: From 7th-13th October, rainfall shall increase: high rainfall is predicted for the western slopes and hills (75–85 mm), Eastern plains and hills and Southern Plains are predicted to receive 45-55mm while the Northern plains are predicted to receive 15-25mm. From 14th-21st October, the rainfall shall intensify further with a similar spatial pattern.
Monitored Rainfall: During 1st-7th October, the average total of rainfall across Sri Lanka was 33mm which was above – normal. Last week rainfall was high from 4th-6th of October. There was more rainfall across the Eastern slopes especially in Moneragala, Badulla, Interior Ampara and Eastern-most Kandy and Matale.
Monitored and Predicted Wind: From 29 September-05 October, winds at 1.5km height were mostly from the West at speeds ranging 6-15 m/s. From 08th-14th October, wind speeds are predicted to be high, in the range of 2-8 m/s still coming from the West and South West.
Monitored Sea and Land Temperature: From 1st-7th October, Temperatures remain seasonable with highest in the Eastern Coast. The sea surface temperature (SST) was warmer than average around Northern, North Western and Eastern coasts by 1 – 1.5 °C. A weak La Niña–type condition is present in the Eastern Pacific; the warm SST around Sri Lanka appear to be muting its typical impacts.
Interpretation
Monitoring
Rainfall: Average Rainfall in the regions for the previous week of (01 October-07 October) = 5 mm/day. Maximum Daily Rainfall: 58.5 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 6-15 m/s from 29 Sep – 05 Oct.
Temperatures: During the period 28 September – 4 October, Sri Lanka experienced above normal temperature anomalies except in Northern, North Central (some areas), North Western (some areas) and part of the western province.
Prediction
Rainfall: From 7– 13 October, rainfall is expected to be 75–85 mm/week in WP region; 65-75 mm/week in WH region; 45-55mm/week in EP, EH and SP regions; 15-25 mm/week in NP region.
Temperatures: From 9-22 October, the temperature will remain above normal in some parts of the EH, NP, EP regions and in Monaragala with maximum temperatures reaching between 33°C and 35°C for Sri Lanka from 09- 22 October (Source SL Met Dept).
Teleconnections: The Madden-Julian-Oscillation (MJO) remains near neutral from 6-10 October and will slightly enhanced for rainfall from 11 – 20 October.
Seasonal Precipitation: The forecast for the October-November-December 2025 season shows high tendency towards the near-neutral tercile despite the emerging La Nina (which lead to lower rainfall) however the temperature is predicted to have high chances of a warm anomaly.
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 |
