Quick answer
The second inter-monsoon is the period between the end of the southwest monsoon and the start of the northeast monsoon, roughly late September to November. With light winds and warm seas, thunderstorms form over the whole island, usually from mid-afternoon into the night. It is the wettest time of year for much of Sri Lanka, with Colombo averaging roughly 330 to 380 mm in October, and Bay of Bengal depressions can bring several wet days in a row.
Key takeaways
- The second inter-monsoon runs roughly from late September to November, until the northeast monsoon takes over.
- Unlike the monsoons, it brings rain to every region, so there is no fully dry coast.
- Rain comes mostly as afternoon and evening thunderstorms, so mornings are often dry.
- October is the wettest month in much of the island, including Colombo and Kandy.
- Depressions and cyclones from the Bay of Bengal are most likely in this period and into December.
What the second inter-monsoon is
The second inter-monsoon is the mirror of the first. In September, the southwest wind weakens. The northeast wind will not settle in until November or December. In between, winds are light and variable, the seas around the island are at their warmest after the summer, and the air is very moist.
As in March and April, daytime heat lifts the moist air into thunderstorms in the afternoon and evening. The difference is that in October and November the air carries more moisture, and weather systems from the Bay of Bengal, such as low-pressure areas and depressions, often add to the storms. The result is the heaviest and most widespread rain of the year.
- →Usual period: late September to November.
- →Wind: light and variable.
- →Rain type: thunderstorms plus passing depressions.
Where it rains most
Every region gets rain, but the southwest and the hills get the most. Colombo averages roughly 330 to 380 mm in October, Kandy roughly 250 to 300 mm and Ratnapura much more. The Cultural Triangle receives its first heavy rain of the season, roughly 150 to 250 mm in October, and the east coast and north follow as the northeast monsoon begins in November.
The hills are where the rain has most effect on travel. Long, heavy rain in October and November is the main trigger for landslides, and warnings for hill roads and parts of the railway are most common in this period.
- →Heaviest: Colombo, Kandy, Ratnapura, the western hills.
- →Heavy later: Trincomalee, Batticaloa, Jaffna in November.
- →First real rain: Sigiriya, Polonnaruwa, Anuradhapura.
The daily rhythm
Most days in the second inter-monsoon follow a pattern. Mornings start clear or partly cloudy, the heat builds towards noon, cloud piles up in the early afternoon, and the storm breaks somewhere between 2 pm and evening. Storms can be intense, with lightning and short-lived flooding on low roads.
When a depression passes close to the island, the pattern breaks. Rain can then fall for one to three days with little pause, often heaviest in the east or north. These events are forecast a few days in advance and are the main reason to keep plans flexible.
Temperatures are moderate: around 29 to 30 °C on the coasts and 20 °C by day in Nuwara Eliya, with high humidity.
The sea and the beaches
Neither coast is reliably calm in the second inter-monsoon. The southwest swell fades in September and October, so the south coast sea becomes calmer, but storms can stir it up. The east coast is often fine early in October and turns rough in November as the northeast wind arrives.
By late November, the south coast usually settles into its dry season, and whale-watching from Mirissa restarts. A beach plan in this period is best placed on the south coast and as late as possible.
- →South coast: calming through October and November.
- →East coast: fine early October, rough from November.
- →Whale-watching from Mirissa restarts around November.
Planning a trip in the second inter-monsoon
Plan by the clock rather than by the map. Start sightseeing early, keep drives short and in the morning, and have indoor plans ready for afternoons: museums in Colombo, tea factories in the hills, temples and cooking classes. Avoid long hill drives after days of heavy rain.
Prices are low and places are quiet. Lankan Stays & Trails plans October and November trips with a spare half day in the hills and checks forecasts before every long drive.
Frequently asked questions
What is the second inter-monsoon in Sri Lanka?
It is the period between the southwest and northeast monsoons, roughly late September to November. Winds are light, the sea is warm and the air is moist, so thunderstorms form across the whole island, usually from mid-afternoon into the night. It is the wettest time of year for much of Sri Lanka.
Why is October so wet in Sri Lanka?
In October there is no monsoon wind to keep one side of the island dry. Daytime heat lifts very moist air into thunderstorms everywhere, and low-pressure systems from the Bay of Bengal add to the rain. Colombo averages roughly 330 to 380 mm in October.
Is there anywhere dry in Sri Lanka in October?
No region is fully dry, but some are drier. The east coast is often drier than the southwest in early October, and the Cultural Triangle gets fewer storms than Colombo or Kandy. Mornings across the island are usually dry, which is the most useful fact for planning.
Are there cyclones during the second inter-monsoon?
Depressions and cyclones in the Bay of Bengal are most common from October to December. Most move towards India, but some pass close to Sri Lanka and bring one to three days of heavy rain and wind, especially to the east and north. Watch forecasts and keep plans flexible.
Is it safe to travel in the hills in October and November?
Generally yes, with care. Long heavy rain can trigger landslides and close hill roads or sections of the railway. Drive in the morning, avoid long hill drives after a day or more of heavy rain, and follow warnings from the National Building Research Organisation.
Is the second inter-monsoon a good time to visit Sri Lanka?
It suits flexible travellers who want quiet places and low prices. Expect afternoon storms almost everywhere and plan sightseeing for mornings. The south coast improves late in November, so a beach finish works best at the end of a trip in that month.
How does Lankan Stays & Trails plan trips in October and November?
Trips in October and November are planned around mornings, with short drives, indoor options for afternoons and a spare half day in the hills. Forecasts are checked before every long drive, and the beach is placed at the end of the trip in late November.