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Climate Bulletin for Sri Lanka (Week of 19 – 26 December 2025)
Highlights
Rainfall Prediction: From 16th -22nd Dec, heavy rainfall (105-135 mm) is predicted for the Eastern plains; fairly heavy rainfall (55-105 mm) is predicted for the Eastern hills , Northern plains, Western plains and hills; light to moderate rainfall (15-55 mm) is predicted for the Southern plains. From 23rd -29th Dec , rainfall is expected to increase, with heavy rainfall (95-135 mm) likely across the country.
Monitored Rainfall:During 09th – 15th November, the average rainfall across Sri Lanka totalled 62 mm. There was fairly heavy rainfall across the Northern plains and Eastern plains especially in Trincomalee with a maximum of 76 mm on 11th December.
Monitored and Predicted Wind: From 08th -14th Dec, winds at 1.5 km height were mostly from the northeast at speeds ranging 5-10 m/s. From 17th-23rd Dec, wind speeds are predicted to be in the range of 3-8 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 31.4°C. The sea surface temperature around Northern and 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 (10-16 December) = 8.9 mm/day. Maximum Daily Rainfall: 76.2 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 08 – 14 Dec.
Wind : During the period 7 – 13 Dec, Sri Lanka experienced near-neutralconditions.
Prediction
Rainfall:From 16 – 22 December, rainfall is expected to be 105–135 mm/week in EP region; 55-105 mm/week in EH, WH, WP and NP regions; 15-55 mm/week in SP region.
Temperatures: From 18 – 31 December, temperature will remain normal for Sri Lanka. (Source: SL Met Dept).
Teleconnections: The Madden-Julian-Oscillation (MJO) will slightly suppress the rainfall from 15th – 19th Dec and slightly enhance the rainfall from 20th – 29th Dec.
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 |
