Blogs
Climate Bulletin for Sri Lanka (Week of 16 – 23 May 2025)
Highlights
Rainfall Prediction: During the next week (14–20 May), ‘fairly heavy’ rainfall (50–100 mm) is predicted for the Central, Western, and Uva provinces, while ‘moderate’ rainfall (25–50 mm) is expected in the Southern, North-Western, Eastern, North-Central, Sabaragamuwa, and Northern provinces.
Monitored Rainfall: Most days in April (14 April – 13 May) recorded above average rainfall. The highest daily rainfall was in Elkaduwa on 06 May (202.0 mm).
Monitored and Predicted Wind: From May 06 to May 12, winds at 850 mb (1.5 km) were from the North-West at speeds ranging between 4 – 10 m/s. From May 15 to May 21, Northwesterly to Westerly winds are expected, with wind speeds ranging from 10 to 15 m/s.
Monitored Sea and Land Temperature: Over the past week, the maximum land surface temperature ranged from 30 °C to 35 °C. The temperature will remain above normal in some parts of the Northern and Eastern . The sea surface temperature around Sri Lanka ranged between 0.25°C – 1.°C above average from 06 May to 12 May, 2025.
Interpretation
Monitoring
Rainfall: Most days in April (14 April – 13 May) recorded above average rainfall. The highest daily rainfall was in Elkaduwa on 06 May (202.0 mm).
Wind: North-Westerly winds prevailed over the sea area and around the island last week, with wind speeds ranging between 4–10 m/s from 06 – 12 May.
Temperatures: Temperature anomalies were near-neutral across Sri Lanka from 04 – 10 May.
Prediction
Rainfall: During the next week (14 May 20 May), “fairly heavy” rainfall (50–100 mm) is predicted for the Central, Western, and Uva while “moderate” rainfall (25-50 mm) is expected in the Southern, North-Western, Eastern, North-Central, Sabaragamuwa, and Northern provinces.
Temperatures: The temperature will remain above normal in some parts of the Northern, and Eastern with maximum temperatures reaching up to 34°C of Sri Lanka from May 16 to May 24.
Teleconnections: The MJO will slightly suppress rainfall from May 14 to May 18, and moderately suppress rainfall from May 19 to 28 May.
Seasonal Precipitation: The precipitation forecast for the May–June–July 2025 season shows a 40% or more tendency toward above normal precipitation of Sri Lanka.
Terminology for Rainfall Ranges
| Terminology | Rainfall (mm/week) |
| Light Showers | Less than 12.5 mm |
| Light to Moderate | Between 12.5 mm and 25 mm |
| Moderate | Between 25 mm and 50 mm |
| Fairly Heavy | Between 50 mm and 100 mm |
| Heavy | Between 100 mm and 150 mm |
| Very Heavy | More than 150 mm |
