Highlights

Monitoring

Rainfall: During 15-21 Sep, Southwestern areas of SL received heavy rainfall exceeding 135 mm. Highest rainfall was in Ratnapura – 98 mm on 19 Sep, Kurunegala – 73 mm & Nuwara Eliya – 48 mm on 20 Sep and Galle – 45mm on 16 Sep. During 16-22 Sep, the average daily rainfall across SL was 8 mm. Wind: From 14-20 Sep 2026, winds at 1.5 km elevation were mostly from the Northwest at speeds of 4-10 m/s. Temperature: Several cities of Eastern Plains had extremely high maximum temperatures exceeding 37°C. Polonnaruwa had the highest temperature of 38.4°C on 19 September and 37.5°C on 18 September. The warmest regions were: Eastern Plains with an average maximum temperature of 34.3°C & Northern Plains with an average maximum temperature of 33.4°C. The coldest region was the Western Hills with an average minimum temperature of 19.7°C.

Predictions

Rainfall: From 22-28 Sep, the US NOAA Climate Prediction Center predicts that the average rainfall across SL shall range from 25-95 mm. During this period, Southern and Western Plains are predicted to receive rainfall of 75-95 mm; Eastern and Western Hills are predicted to receive 45-75 mm; Northern and Eastern Plains are predicted to receive 25-45 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 23-29 Sep 2026, winds are predicted to speed up to 8-15 m/s, arriving mainly from the westerly directions including 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 3.0°C above average. Indian Ocean (IO) SST: The IO Dipole Mode Index (DMI) is at +0.2°C, indicating neutral IO Dipole conditions. 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

From 22-28 Sep, 75-95 mm is predicted for the Southern and Western Plains; 45-75 mm is predicted for the Eastern and Western Hills; 25-45 mm is predicted for the Northern and Eastern Plains.  From 29 Sep-5 Oct, 85-135 mm is predicted for the Southern and Western Plains; 25-85 mm is predicted for the rest of SL.

(Source: NOAA CPC)

Monitored Rainfall

During 15-21 Sep, Southwestern areas of SL received heavy rainfall exceeding 135 mm. (Source: NOAA CPC) The highest rainfall was recorded in Ratnapura – 98 mm on 19 Sep, Kurunegala – 73 mm and Nuwara Eliya – 48 mm on 20 Sep, and Galle – 45 mm on 16 Sep. During 16-22 Sep, the average daily rainfall across SL was 8 mm.

Monitored Land & Sea Temperature

During 16-22 Sep, average maximum temperature in SL was 31.5°C, lower than the previous week (33.0°C). The Eastern Plains was the warmest, at 34.3°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°C around the rest of the coasts.

Monitored & Predicted Wind

From 14-20 Sep 2026, winds at 1.5 km elevation were mostly from the Northwest, at speeds of 4-10 m/s. From 23-29 Sep 2026, winds are predicted to speed up to 8-15 m/s, arriving mainly from the westerly directions, including Northwest & Southwest.