Blogs
Climate Bulletin for Sri Lanka (Week of 26 September – 03 October 2025)
Highlights
Rainfall Prediction: Sri Lanka is reaching the end of its dry season. From 23rd to 29th September, rainfall is expected to be 35–45 mm in Central, Western and Sabaragamuwa provinces; 25-35 mm in North-Central and North-Western provinces; 15-25 mm in Northern, Eastern and Uva provinces; 5-15 mm in Southern province.
Monitored Rainfall: Notable rainfall was recorded on 17th and 18th September. The 30 day rainfall total as of 21st September was around 90mm, compared to an expected normal of about 75mm, showing that totals shifted from a below normal level earlier in the month to above normal rainfall after mid September.
Monitored and Predicted Wind: From 15-21 September, winds at 1.5 km height were mostly from the West at speeds ranging 5-10 m/s From 24-30 September, wind speeds are predicted to be high, in the range of 5-20 m/s coming from the North-West.
Monitored Sea and Land Temperature: Average maximum land surface temperature was 30.8 °C during 16 – 23 September. The Oluvil Station was the warmest, followed by Trincomalee and Hambantota stations. From 15–21 September, the sea surface temperature was above average around Northern, North Western, Western and Eastern coasts.
Interpretation
Monitoring
Rainfall: Average Rainfall in the regions for the previous week of (16 September-23 September) = 2.46 mm/day. Maximum Daily Rainfall: 15.00 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 5-10 m/s from 15-21 September.
Temperatures: From September 14 to 20, Sri Lanka experienced near neutral temperature anomalies, except in part of the Southern province.
Prediction
Rainfall: During the next week, rainfall is expected to be 35–45 mm/week in Central, Western and Sabaragamuwa provinces; 25-35 mm/week in North-Central and North-Western provinces; 15-25 mm/week in Northern, Eastern and Uva provinces; 5-15 mm/week in Southern province.
Temperatures: The temperature will remain above normal in some parts of the Northern, North-Central, Uva, Southern, Eastern, Central, Sabaragamuwa and North-Western provinces and in Monaragala with maximum temperatures reaching between 34°C and 38°C of Sri Lanka from 25 September – 08 October.
Teleconnections: The MJO will remain in a near-neutral phase regarding rainfall from September 23 – October 07.
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 |
