Highlights

Predictions

Rainfall: During Oct-Dec, there is a 50% likelihood of SL receiving higher-than-normal tercile rainfall (Source: CCSR/IRI multi-model Probability prediction). From 6-12 Oct, the US NOAA Climate Prediction Center predicts that the average rainfall across SL shall range from 25-115 mm. During this period, Western Hills,Southern and Western Plains are predicted to receive rainfall of 85-115 mm; Eastern Hills and Plains are predicted to receive 45-85 mm; Northern Plains are predicted to receive 25-45 mm.  Wind: From 7-13 Oct 2026, winds are predicted to be in similar speeds of 1-4 m/s, arriving mostly from the Northeast. 

Monitoring

Rainfall:Rainfall was higher in the North-Western, Sabaragamuwa and Central of Sri Lanka. Highest average rainfall was in Western Hills – 8.4 mm and Eastern Hills – 6 mm.During 30 Sep – 6 Oct, the average daily rainfall across SL was 4.7 mm. Wind: From 28 Sep – 4 Oct 2026, winds at 1.5 km elevation were mostly from the West at  speeds of 1-4 m/s. Temperature: Several cities of Eastern Plains had  high maximum temperatures exceeding 37°C. Polonnaruwa and Vavuniya had the highest temperature of 37.5°C on 30 September. The warmest regions were: Northern Plains with  an average maximum temperature of 34.2°C & Eastern Plains with an average maximum temperature of 34.1°C. The coldest region at night was the Eastern Hills with an average minimum temperature of 18.6°C. 

Indian Ocean (IO) SST

According to CCSR/IRI climate forecasts, there is 90-95% probability of a positive IOD from October through December 2026. The IOD (Indian Ocean Dipole) has established into a positive phase this week, with the Dipole Mode Index (DMI) reaching +0.68°C. The DMI has increased from +0.2°C in September, indicating a strengthening of the positive IOD conditions. A positive dipole event is identified at DMI > 0.4. El Niño Event: El Niño conditions continue to prevail across the equatorial Pacific Ocean (Niño 3.4 region). Currently, sea surface temperature (SST) in the Niño 3.4 region is 3.0°C above average – this is one of the strongest El Nino events already. 

Rainfall Prediction

Rainfall is predicted to increase, particularly in the South-West of SL. From 6–12 Oct, 85–115 mm is predicted for the Western Hills, Southern and Western Plains; 45–85 mm is predicted for the Eastern Hills and Plains; 25–45 mm is predicted for the Northern Plains. From 13–19 Oct, 105–135 mm is predicted for the Southern and Western Plains; 35–105 mm is predicted for the rest of SL. (Source: NOAA CPC)

Monitored Rainfall

Overall, SL received above-normal rainfall during the first week of October (daily average: 7–11 mm). Rainfall was higher in the North-Western, Sabaragamuwa, and Central regions of Sri Lanka. The highest average rainfall was recorded in the Western Hills (8.4 mm) and Eastern Hills (6 mm). During 30 September–6 October, the average daily rainfall across SL was 4.7 mm.

Monitored Land & Sea Temperature

Temperature continued to be warmer, particularly during the daytime in Northern and Eastern SL. During 30 Sep–6 Oct, the average maximum temperature in SL was 32.6°C, higher than the previous week’s average of 32.0°C. The sea surface temperature around SL was 1.5–2.0°C warmer than the seasonal average around the Western coasts and 0.5–1.5°C warmer around the rest of the coasts.

Monitored & Predicted Wind

The winds during the last week were from the West at low speeds. Predictions for the coming week show a shift in wind direction from westerly to north-easterly winds. From 28 Sep–4 Oct 2026, winds at 1.5 km elevation were mostly from the West, at speeds of 1–4 m/s. From 7–13 Oct 2026, winds are predicted to maintain similar speeds of 1–4 m/s, arriving mostly from the Northeast.