Blogs
Climate Bulletin for Sri Lanka (Week of 26 December – 02 January 2025)
Highlights
Rainfall Prediction:From 23rd -29th Dec, fairly heavy rainfall (55-95 mm) is predicted for the Eastern plains and Hills, Northern Plains and Western Hills ; light to moderate rainfall (05-55 mm) is predicted for the Western Plains and Southern plains.From 30th Dec-05th Jan , heavy rainfall (105-135 mm) is predicted for Western Plains and Hills, Eastern Plains and Hills, Northern Plains.
Monitored Rainfall:During 16th – 22nd December, the average rainfall across Sri Lanka totalled 48 mm. There was fairly heavy rainfall across the Western plains especially in Galle with a maximum of 106 mm on 20th December.
Monitored and Predicted Wind: From 15th -21st Dec, winds at 1.5 km height were mostly from the northeast at speeds ranging 5-10 m/s. From 24th-30th Dec, wind speeds are predicted to be in the range of 1-5 m/s coming from the North East.
Monitored Sea and Land Temperature: Sri Lanka recorded seasonable temp across its regions. The Southern plains were the warmest, with maximum temp of 30.5°C. The sea surface temperature around Northern, Eastern and South Eastern coasts, was below average, ranging between -1°C and 0.25°C
Interpretation
Monitoring:Average Rainfall in the regions for the previous week of (17-23 December) = 6.9 mm/day. Maximum Daily Rainfall: 105.5 mm & Minimum Daily Rainfall: 0.0 mm.
Rainfall: North-Easterly winds prevailed over the sea area and around the island last week, with wind speeds ranging between 5-10 m/s from 15 – 21 Dec.
Wind :During the period 14 – 20 Dec, Sri Lanka experienced near-neutral conditions.
Prediction
Rainfall: From 23 – 29 December, rainfall is expected to be 55–95 mm/week in NP, EP, WH, EH regions; 05-55 mm/week in SP, WP regions.
Temperatures: From 25 December – 07 January, temperature will remain normal for Sri Lanka. (Source: SL Met Dept).
Teleconnections: The Madden-Julian-Oscillation (MJO) will be near neutral from 22nd – 26th Dec, slightly enhance the rainfall from 27th – 31st Dec 2025 and moderately enhance the rainfall from 1st – 5th January 2026.
Seasonal Rainfall Prediction: The forecast for the January-February-March 2026 season shows high tendency towards the near-neutral tercile.
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 |
