Quick answer
The west coast of Sri Lanka, from Negombo through Colombo to Bentota and Beruwala, is driest and calmest roughly from December to March, with January and February the driest months. It is wet and rough from about late May to September, during the southwest monsoon, and stormy in April and from October to November, the two inter-monsoon periods. Temperatures stay around 29 to 31 °C by day all year, and the sea is about 27 to 29 °C.
Key takeaways
- The west coast is driest and calmest roughly from December to March.
- The southwest monsoon brings rain and rough seas from roughly late May to September.
- April and October to November bring heavy afternoon and evening storms.
- Daytime temperatures barely change, around 29 to 31 °C all year.
- The west coast is wetter than the far south coast and much wetter than the east coast.
The stretch this covers
The west coast runs roughly from Negombo, near the airport, south through Colombo, Mount Lavinia, Wadduwa and Kalutara to Beruwala, Bentota and Induruwa, where it bends into the south coast. It sits fully in the wet zone and faces the southwest monsoon head on.
The coast is flat and low, with lagoons at Negombo, river mouths at Kalutara and Bentota, and long open beaches rather than sheltered bays. That shape matters for the sea, because few beaches have a headland or reef to break the monsoon swell.
Rainfall decreases slightly from south to north. Negombo is a little drier than Colombo, and Kalutara, closer to the rainforest hills, is wetter.
- →Negombo: slightly drier than Colombo.
- →Colombo and Mount Lavinia: the reference station.
- →Kalutara, Beruwala, Bentota: slightly wetter.
The dry season: December to March
From about December to March, the northeast monsoon leaves the west coast in a rain shadow. January and February are the driest months, with roughly 60 to 100 mm of rain in Colombo, mostly in short showers. December can still bring early storms, and March brings the first inter-monsoon thunderstorms late in the month.
The sea is calm, and long beaches such as Bentota, Induruwa and Wadduwa are at their best for swimming and river trips. Humidity is lower than at any other time, and evenings are pleasant.
- →Driest: January and February.
- →Calm sea: roughly December to April.
- →Lowest humidity of the year.
The monsoon months: May to September
The southwest monsoon usually arrives in the second half of May. Late May and June are the wettest weeks, with Colombo averaging roughly 300 to 380 mm in May. July and August are lighter, often with long sunny spells between showers, and September brings a return of afternoon storms.
The sea is rough throughout, with swell, strong currents and red flags on most open beaches. That makes the west coast in the monsoon better for city sightseeing, food, Ayurveda and the Bentota river than for swimming.
The wind is steady and the humidity high, but temperatures fall slightly, to about 29 to 30 °C.
- →Wettest: late May and June.
- →Lighter: July and August.
- →Sea: rough throughout.
The storm months: April, October and November
The two inter-monsoon periods bring a different kind of rain. In April, and again in October and November, light winds allow afternoon heat to build into heavy thunderstorms. Colombo averages roughly 200 to 250 mm in April and roughly 300 to 380 mm in October, one of its wettest months.
Mornings in these months are usually bright, and the sea is calmer than in the monsoon, especially in April. Storms can cause short-lived flooding on low roads in Colombo.
- →April: hot, storms in the afternoons.
- →October: one of the wettest months.
- →November: storms early, drying late.
Using west coast weather
For a first or last night near the airport, the west coast works all year, because the hotels and the city do not depend on the beach. For a beach stay, plan December to April. From May to September, use the east coast for swimming and keep the west coast for Colombo and Bentota's river.
Lankan Stays & Trails books west coast beach stays from December to April and uses Negombo and Colombo as all-year arrival and departure bases.
Frequently asked questions
What is the best time to visit the west coast of Sri Lanka?
For the beach, roughly December to April, when the west coast is dry and the sea is calm, with January and February the driest months. For Colombo and Negombo as arrival bases, any month works, because city sights, food and hotels do not depend on the weather.
When is the rainy season on the west coast of Sri Lanka?
The main rainy season is the southwest monsoon, from roughly late May to September, wettest in late May and June. The west coast also gets heavy inter-monsoon storms in April and from October to November, with October one of Colombo's wettest months.
Is the sea calm on the west coast in June?
No. The southwest monsoon brings swell and strong currents to the west coast from late May to September, and most open beaches fly red flags. Bentota, Wadduwa and Mount Lavinia are not safe for swimming in June. The east coast is calm at that time.
Is Negombo drier than Colombo?
Slightly. Negombo, about 35 km north of Colombo, receives a little less rain on average, but it follows the same seasons: driest from December to March, wet in the southwest monsoon and stormy in April and October to November.
How hot is the west coast of Sri Lanka?
Daytime temperatures stay around 29 to 31 °C all year, with nights around 23 to 26 °C. April is the hottest and most humid month. The sea is roughly 27 to 29 °C year-round, so there is no cold season, only wet and dry ones.
Is Bentota good in the monsoon?
Bentota is good for its river, mangrove boat trips, Lunuganga and quiet hotels in the monsoon, but not for swimming, because the sea is rough from late May to September. Its beach season runs from about December to April.
How does Lankan Stays & Trails use the west coast in different seasons?
West coast beach stays are planned from December to April. In the monsoon months, Negombo and Colombo serve as arrival and departure bases, and Bentota is used for river trips and rest rather than swimming, with beach time moved to the east coast.