Highlights

Predictions

Rainfall:  From 20-26 Oct, the US NOAA Climate Prediction Center predicts that the SL shall receive extremely heavy rainfall exceeding 135 mm. During Oct-Dec, there is a 50% likelihood of SL receiving higher-than-normal tercile rainfall (Source: CCSR/IRI multi-model Probability prediction). ECMWF predicts heavy rainfall of 50-80 mm for northern, western and central regions from 23-26 Oct.Wind: From 21-27 Oct 2026, winds are predicted to speed up to 6-15 m/s, arriving mostly from the West and South-West. The predictions for the coming week shows a dramatic speeding up

Monitoring

Rainfall:During 13-19 Oct, there was extremely heavy rainfall in western, central and eastern regions, with Polonnaruwa receiving the highest daily rainfall of 146 mm on 17 Oct. Highest average rainfall was in Western Hills – 18.4 mm and Northern Plains – 16.8 mm.During 14-20 Oct, the average daily rainfall across SL was 15.4 mm. Wind: From 12-18 Oct 2026, winds at 1.5 km elevation were mostly from the South-West at  speeds of 1-3 m/s. Temperature: Overall, temperature was typical for October across SL, with Eastern Hills being relatively cooler (27.4°C). The warmest region was Eastern Plains with  an average maximum temperature of 32.5°C. The coldest region at night was the Eastern Hills with an average minimum temperature of 19.1°C. 

Cyclonic Systems

Two cyclonic systems are being monitored in the surrounding seas and are expected to remain active until 26 October. Neither system is moving towards Sri Lanka. However, their wind patterns may influence the island’s weather, potentially increasing rainfall over the mountain slopes.

Indian Ocean (IO) SST

According to CCSR/IRI climate forecasts, there is 75-95% probability of a positive IOD from November through December 2026. The Dipole Mode Index (DMI) of the current positive IOD (Indian Ocean Dipole) phase has increased to +0.88°C from +0.76°C last week, indicating a strengthening of the positive IOD conditions. A positive dipole event is identified at DMI > 0.4.

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 3.3°C above average – this is one of the strongest El Nino events.

Rainfall Prediction

From 20–26 Oct, SL is predicted to receive extremely heavy rainfall exceeding 135 mm. Rainfall exceeding 135 mm is predicted for the Western and Eastern Hills and the Southern, Eastern, Northern and Western Plains. ECMWF predicts heavy rainfall of 50–80 mm for the Northern, Western and Central regions from 23–26 Oct. From 27 Oct–2 Nov, 95–125 mm is predicted for the Western Hills, Southern and Western Plains.

Monitored Rainfall

During 13–19 Oct, there was extremely heavy rainfall in the Western, Central and Eastern regions, with Polonnaruwa recording the highest daily rainfall of 146 mm on 17 Oct. The highest average rainfall was recorded in the Western Hills (18.4 mm) and Northern Plains (16.8 mm). During 14–20 Oct, the average daily rainfall across SL was 15.4 mm.

Monitored Land & Sea Temperature

Overall, temperature was typical for October across SL, with the Eastern Hills being relatively cooler (27.4°C). During 14–20 Oct, the average maximum temperature in SL was 31.2°C, lower than the previous week’s average of 31.8°C. The sea surface temperature around SL was 1.5–2.0°C warmer than the seasonal average around the Western coasts and 1.0–1.5°C warmer around the rest of the coasts.

Monitored & Predicted Wind

The winds during the last week were from the South-West at low speeds. Predictions for the coming week show a dramatic increase in wind speeds. From 12–18 Oct 2026, winds at 1.5 km elevation were mostly from the South-West, at speeds of 1–3 m/s. From 21–27 Oct 2026, winds are predicted to speed up to 6–15 m/s, arriving mostly from the West and South-West.