Highlights

Monitoring

Rainfall: After a dry week, rainfall picked up on 13 Sep with daily average reaching 16 mm. However, Southwest areas received heavy rainfall with Galle reaching 132 mm. Nearby areas also received moderate rainfall, with Ratmalana reaching 62 mm on 14 Sep and Katunayaka reaching 59 mm on 12 Sep. During 9-15 Sep, the average daily rainfall across SL was 6 mm. Wind: From 7 – 13 Sep 2026, winds at 1.5 km elevation were mostly from the West at speeds of 6-8 m/s. Temperature: Several cities of Eastern and Northern Plains had extremely high maximum temperatures exceeding 38°C. Polonnaruwa had the highest temperature of 39.3°C on 12 September and 38.9°C on 11 September. The warmest regions were: Eastern Plains with an average maximum temperature of 35.5°C & Northern Plains with an average maximum temperature of 34.8°C. The coldest region was the Western Hills with an average minimum temperature of 19.7°C.

Predictions

Rainfall: From 15-21 Sep, the US NOAA Climate Prediction Center predicts that the average rainfall across SL shall range from 25-125 mm. During this period, Southern and Western Plains are predicted to receive rainfall of 105-125 mm; Eastern and Western Hills are predicted to receive 55-105 mm; Northern and Eastern Plains are predicted to receive 25-55 mm. According to CCSR/IRI Multi-Model Probability prediction, there is a 50% likelihood of SL receiving higher-than-normal tercile rainfall during October-December. Wind: From 16–22 Sep 2026, winds are predicted to slow down to 4-8 m/s and arrive from the Northwest & 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 2.7°C above average. Indian Ocean (IO) SST: The IO Dipole Mode Index (DMI) is at +0.11°C, indicating neutral IO Dipole conditions. Positive dipole event is identified at DMI > 0.4. According to CCSR/IRI climate forecasts, there is 80-90% probability of a positive IOD from September through December 2026.

Rainfall Prediction

From 15–21 Sep, 105–125 mm is predicted for the Southern and Western Plains; 55–105 mm is predicted for the Eastern and Western Hills; 25–55 mm is predicted for the Northern and Eastern Plains.From 22–28 Sep, 55–65 mm is predicted for the Eastern and Western Plains; 5–55 mm is predicted for the rest of SL.

(Source: NOAA CPC)

Monitored Rainfall

After a dry week, rainfall picked up on 13 Sep, with the daily average reaching 16 mm. However, Southwest areas received heavy rainfall, with Galle reaching 132 mm. Nearby areas also received moderate rainfall, with Ratmalana reaching 62 mm on 14 Sep and Katunayaka reaching 59 mm on 12 Sep. During 9–15 Sep, the average daily rainfall across SL was 6 mm.

Monitored Land & Sea Temperature

During 9–15 Sep, average maximum temperature in SL was 33.0°C, lower than the previous week (33.2°C). The Eastern Plains was the warmest, at 35.5°C. The sea surface temperature around SL was warmer than the seasonal average by 1.5–2°C around the Northern, Eastern and Western coasts, and by 1.0°C around the rest of the coasts.

Monitored & Predicted Wind

From 7–13 Sep 2026, winds at 1.5 km elevation were mostly from the West, at speeds of 6–8 m/s. From 16–22 Sep 2026, winds are predicted to slow down to 4–8 m/s and arrive from the Northwest & Southwest.