Highlights

Monitoring

Heavy rainfall over the western slopes during 1–4 August negated the dry conditions predicted for July and August by several agencies. Following these heavy rainfall events, SL experienced a relatively dry period from 5-10 Aug with daily average rainfall ranging from 1-5 mm. During 5-11 Aug, the average daily rainfall across SL was 2.4 mm. The highest daily rainfall was in Mullaitivu – 49 mm on 8 Aug, Ratnapura – 22 mm on 9 Aug and Galle – 22 mm on 7 Aug. From 3-9 Aug 2026, winds at 1.5 km elevation were mostly from the Northwest at 10-15 m/s. Overall the  temperature was typical for July across SL. The Eastern Plains had an average maximum temperature of 35.0°C. The Eastern Hills had an average minimum temperature of19.1°C.

Predictions

From 4-10 Aug, the US NOAA Climate Prediction Center predicts that the overall rainfall across SL shall increase compared to the previous week. During this period; Eastern Plains are predicted to receive rainfall of 35-55 mm. From 12-18 Aug, wind speeds are predicted to be 4-10 m/s from the Northwest & West.

El Niño Event

El Niño conditions continue to prevail across the equatorial Pacific Ocean (Niño 3.4 region). Currently, sea surface temperature in the Niño 3.4 region are around 2.1°C above average. Meanwhile, the Indian Ocean is gradually transitioning towards a positive IOD phase, which is typically associated with El Niño. According to CCSR/IRI Multi-Model Probability Forecast, Sri Lanka is expected to receive much heavier rainfall than usual from August onwards. The likelihood increases from 45% during August-October to 60% during September-November.

Rainfall Prediction

From 11–17 Aug; 35–55 mm is predicted for the Eastern Plains; 15–35 mm is predicted for the Western Hills & Plains, Eastern Hills and Southern Plains; 0–5 mm is predicted for the Northern Plains. From 18–24 Aug, rainfall shall be similar to the previous week: 35–45 mm is predicted for the Eastern Plains and Western Hills; 5–35 mm is predicted for the rest of Sri Lanka.
(Source: NOAA CPC)

Monitored Rainfall

Following the heavy rainfall experienced across the western slopes from 1–4 Aug, SL experienced a relatively dry period from 5–10 Aug with daily average rainfall ranging from 1–5 mm. During 5–11 Aug, the average daily rainfall across SL was 2.4 mm. Highest daily rainfall was in Mullaitivu – 49 mm on 8 Aug, Ratnapura – 22 mm on 9 Aug, and Galle – 22 mm on 7 Aug.

Monitored Land & Sea Temperature

During 5–11 Aug, average maximum temperature in Sri Lanka was 31.7°C, lower compared to the previous week (32.0°C). The Western Hills was the coolest, at 25.6°C. The sea surface temperature around SL was warmer by 1.5°C around the northern, eastern and western coasts, and cooler by 0.5°C around the southern coasts.

Monitored & Predicted Wind

From 3–9 Aug 2026, winds at 1.5 km elevation were mostly from the Northwest, at speeds of 10–15 m/s. From 12–18 Aug 2026, winds are predicted to slow down to 4–10 m/s and arrive from the Northwest & West.