Highlights

Monitoring

Rainfall: Rainfall continued to be high in the South-West of Sri Lanka alone. Highest rainfall was in Mattala – 70 mm on 23 Sep, Bandarawela – 53 mm on 29 Sep and Ratnapura – 44 mm on 24 Sep. During 23-29 Sep, the average daily rainfall across SL was 4.6 mm. Wind: From 21-27 Sep 2026, winds at 1.5 km elevation were mostly from the Northwest and West at speeds of 10-15 m/s. Temperature: Several cities of Eastern Plains had high maximum temperatures exceeding 37°C. Polonnaruwa had the highest temperature of 38.3°C, followed by Moneragala at 37.9°C and Vavuniya at 37.8°C on 27 September. The warmest regions were: Eastern Plains with an average maximum temperature of 35.2°C & Northern Plains with an average maximum temperature of 34.0°C. The coldest region at night was the Eastern Hills with an average minimum temperature of 19.6°C.

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 29 Sep – 5 Oct, the US NOAA Climate Prediction Center predicts that the average rainfall across SL shall range from 25-105 mm. During this period, Southern and Western Plains are predicted to receive rainfall of 85-105 mm; Eastern and Western Hills are predicted to receive 55-85 mm; Northern and Eastern Plains are predicted to receive 25-55 mm. Wind: From 30 Sep – 6 Oct 2026, winds are predicted to slow down to 2-4 m/s, arriving mostly from the Southwest.

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. Indian Ocean (IO) SST: The IO Dipole Mode Index (DMI) is at +0.2°C, indicating neutral IO Dipole conditions. A positive dipole event is identified at DMI > 0.4. According to CCSR/IRI climate forecasts, there is 90-95% probability of a positive IOD from September through December 2026

Rainfall Prediction

Rainfall is predicted to increase, particularly in the South-West of SL. From 29 Sep-5 Oct, 85-105 mm is predicted for the Southern and Western Plains; 55-85 mm is predicted for the Eastern and Western Hills; 25-55 mm is predicted for the Northern and Eastern Plains. From 6-12 Oct, 95-115 mm is predicted for the Southern and Western Plains; 25-95 mm is predicted for the rest of SL. 

(Source: NOAA CPC)

Monitored Rainfall

Rainfall continued to be high in the South-West of Sri Lanka. Overall, SL received above-normal rainfall during the last two weeks of Sep, with a daily average of 5-16 mm. The highest rainfall was recorded in Mattala – 70 mm on 23 Sep, Bandarawela – 53 mm on 29 Sep, and Ratnapura – 44 mm on 24 Sep. During 23-29 Sep, the average daily rainfall across SL was 4.6 mm.

Monitored Land & Sea Temperature

Temperature continued to be warmer, particularly during the daytime in Eastern SL. During 23-29 Sep, average maximum temperature in SL was 32.0°C, higher than the previous week (31.5°C). The sea surface temperature around SL was warmer than the seasonal average by 1.0-1.5°C around the Northern, Eastern and Western coasts, and by 0.5-1.0°C around the rest of the coasts.

Monitored & Predicted Wind

The wind in the last few weeks was from the West and Northwest at high speeds. Predictions for the coming week show a dramatic slowdown. From 21-27 Sep 2026, winds at 1.5 km elevation were mostly from the Northwest and West, at speeds of 10-15 m/s. From 30 Sep-6 Oct 2026, winds are predicted to slow down significantly to 2-4 m/s, arriving mostly from the Southwest.