Quick answer
The southwest monsoon usually fades through September, giving way to the inter-monsoon storms of October, and the south and west coasts settle into their dry season in late November or December. The northeast monsoon usually eases through January and ends by February, but the sea on the east coast often stays rough until March. In both cases the rain stops a few weeks before the sea becomes reliably calm.
Key takeaways
- The southwest monsoon usually fades through September, but the southwest coast is not fully dry until late November or December.
- The northeast monsoon usually eases in January and ends by February.
- The sea takes longer to settle than the rain: the east coast often stays rough until March.
- Each monsoon is followed by an inter-monsoon period of afternoon storms, not by instant dry weather.
- The weeks just after a monsoon are good value, with lower prices and fresh green landscapes.
The end of the southwest monsoon
The southwest monsoon usually weakens through September. The steady wind becomes less reliable, the showers on the west coast become less frequent, and the swell on the south coast slowly falls. By the end of September, the monsoon has usually withdrawn.
That does not mean the southwest coast is dry. The second inter-monsoon follows, bringing heavy afternoon storms through October and much of November. Colombo's wettest months are often May and October, either side of the monsoon. The southwest coast only settles into its long dry season when the northeast monsoon is established, usually in the second half of November or early December.
For the sea, the timeline is similar. Swell drops through October, and by late November the south coast bays are usually calm enough for swimming and whale-watching from Mirissa restarts.
- →Monsoon fades: through September.
- →Inter-monsoon storms: October and much of November.
- →Southwest dry season begins: late November to December.
The end of the northeast monsoon
The northeast monsoon usually eases through January. Rain on the east coast and in the north becomes lighter and less frequent, and by February many days are dry and sunny. The monsoon is generally over by the end of February.
The sea is slower. The northeast wind often keeps pushing swell onto the east coast through February, and Nilaveli, Uppuveli and Pasikudah usually become reliably calm only in March. Many east coast beach hotels reopen fully in March or April, and Arugam Bay's surf season starts in April or May.
- →Rain eases: January.
- →Monsoon ends: usually by late February.
- →East coast sea calm: usually from March.
Why the sea lags behind the rain
The reason the sea lags is that swell is made by wind over long distances of ocean, not by local rain. Even after the rain clouds have gone, the monsoon wind keeps blowing for weeks and keeps pushing waves onto the coast that faces it. The sea calms only when the wind itself drops or changes direction.
That is why the best guide to a beach trip near the end of a season is the wind, not the rain. When the wind on a coast drops or swings to blow off the land, the sea follows within days.
- →Rain stops first.
- →Wind drops next.
- →Sea calms last.
Travelling just after a monsoon
The weeks after a monsoon have their attractions. The landscape is green, waterfalls are full, the dust has settled, and hotels have not yet moved to peak prices. Late November and early December on the south coast, and March on the east coast, are good examples.
The trade-off is uncertainty. A late burst of rain or a lingering swell is possible, so flexible bookings and a plan B for the beach days are worth having.
Planning around the end of the monsoon
Put beach time at the end of the trip if it falls just after a monsoon, so the sea has as long as possible to settle. Check the wind and swell forecast in the week before, and choose a sheltered bay rather than an exposed beach.
Lankan Stays & Trails plans post-monsoon trips with the beach at the end and checks the wind forecast before confirming beach nights.
Frequently asked questions
When does the monsoon end in Sri Lanka?
The southwest monsoon usually fades through September, and the northeast monsoon usually eases in January and ends by February. Each is followed by an inter-monsoon period of afternoon storms. The southwest coast is fully dry from late November or December, and the east coast sea is calm from about March.
When does the rainy season end on the south coast of Sri Lanka?
The southwest monsoon fades in September, but the south coast has inter-monsoon storms through October and much of November. It usually settles into its dry season in the second half of November or early December, when the northeast monsoon is established.
When does the rainy season end on the east coast of Sri Lanka?
Rain on the east coast usually eases in January and the northeast monsoon is generally over by February. The sea often stays rough into early March, so the east coast beach season is usually counted from March or April to September.
When does the sea calm down in Sri Lanka?
On the south and west coasts, the sea usually calms in late November or December. On the east coast, it usually calms in March. In both cases the sea settles a few weeks after the rain eases, because the monsoon wind keeps pushing swell onto the coast.
Is it good to travel just after the monsoon?
Often, yes. The landscape is green, waterfalls are full and prices are lower before peak season. The risk is a late burst of rain or a lingering swell, so flexible bookings and a plan B for beach days are useful.
Is September the end of the rainy season in Sri Lanka?
September is the end of the southwest monsoon, but not of the rain. The second inter-monsoon follows in October and November, which is the wettest period for much of the island. The southwest's dry season usually begins only in the second half of November.
How does Lankan Stays & Trails plan trips just after a monsoon?
Beach nights are placed at the end of the trip so the sea has time to settle, sheltered bays are chosen over exposed beaches, and the wind and swell forecast is checked in the week before travel. Flexible bookings are recommended near the change of season.