Highlights

Monitoring 

From 1–4 August, the western slopes experienced extreme weather conditions, with several hydro catchment areas receiving over 200 mm of rainfall: Norton – 259 mm, Canyon – 235 mm, Lakshapana – 208 mm on 3 Aug | Canyon – 191 mm, Lakshapana – 187 mm, Norton – 186 mm on 2 Aug. The severe weather experienced during 1–4 August was consistent with last week’s forecast, which predicted 55–85 mm of rainfall over the Western slopes. During 29 July – 4 Aug, the average daily rainfall was 5.6 mm. Among the other Met stations, the highest daily rainfall was in Nuwara Eliya – 94 mm on 2 Aug & 72 mm on 5 Aug, Batticaloa – 73 mm on 5 Aug. From 27 July – 2 Aug 2026, winds at 1.5 km elevation were mostly from the West at 10-20 m/s. Overall the temperature was typical for July across SL. The Eastern Plains had an average maximum temperature of 35.4°C. The Eastern Hills had an average minimum temperature of 20.2°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; Western Hills, Western & Southern Plains are predicted to receive rainfall of 35-55 mm. From 5-11 Augwind speeds are predicted to be 5-15 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. 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 from45% during August-October to 70% during September-November. This unusually wet weather is caused by the El Niño influence.

Rainfall Prediction

From 4 – 10 Aug: 35-55 mm is predicted for the Western Hills, Western & Southern Plains: 25-35 mm is predicted for the Northern Hills, Eastern Hills & Plains.
From 11-17 Aug, rainfall shall decrease compared to the previous week: 25-35 mm is predicted for the Western & Southern Plains. 5-25 mm is predicted for the rest of Sri Lanka.

(Source: NOAA CPC)

Monitored Rainfall

From 1–4 August, the western slopes experienced extreme weather conditions, with several hydro catchment areas receiving over 200 mm of rainfall : Norton – 259 mm, Canyon – 235 mm, Lakshapana – 208 mm on 3 Aug. During 29 July – 4 August, the average daily rainfall across Sri Lanka was 5.6 mm.

Monitored Land & Sea Temperature

During 29 July – 4 Aug, average maximum temp in SL was 32.0°C. lower compared to the previous week – 33.0°C. The Eastern Plains was warmest – 35.4°C. The sea surface temperature around SL was warmer by 1.5°C around northern, eastern and western coasts and cooler around northeastern and southern coasts

Monitored & Predicted Wind

From 27 Jul – 2 Aug 2026, winds at 1.5 km elevation were mostly from the West at speeds of 10 – 20 m/s. From 5 – 11 Aug 2026, winds are predicted to slow down to 5-15 m/s and arrive from the Northwest & West.