Quick answer
In May the southwest monsoon arrives, usually in the second half of the month, bringing heavy rain, wind and rough seas to the west and south coasts and the western hills. Colombo averages roughly 300 to 380 mm, often its wettest month. The east coast and the north stay dry, hot and calm, with Trincomalee averaging only about 50 to 100 mm, and the Cultural Triangle is hot with occasional showers.
Key takeaways
- May is often Colombo's wettest month, as the southwest monsoon arrives on the west and south coasts.
- The monsoon usually sets in during the second half of May; the first weeks often feel like April.
- The sea on the west and south coasts becomes rough, and many beaches fly red flags from late May.
- The east coast and the north are dry and calm, so May is the start of their best season.
- Hill country rain falls mostly on the western slopes; Ella and the Uva side stay drier.
May at a glance
May is the month the wind changes. The light, variable winds of the first inter-monsoon give way to the southwest monsoon, a steady wind from the Indian Ocean that brings rain to the southwest quarter of the island and pushes swell onto its beaches. The date varies from year to year, but the third or fourth week of May is typical.
Before the onset, May feels like a hotter April, with clear mornings and afternoon storms. After it, the southwest coast has days of cloud, gusty wind and bursts of heavy rain, broken by sunny spells. The east and north, in the rain shadow of the hills, become dry, hot and breezy.
For a visitor, the practical change is that the beach side of the island switches. From late May the swimming is on the east coast, while the south and west are better for scenery, food and culture than for the sea.
- →West and south coasts: monsoon onset, heavy rain, rough sea.
- →Hill country: wet western slopes, drier Ella side.
- →Cultural Triangle: hot, mostly dry, some showers.
- →East coast and north: dry, calm, in season.
The west and south coasts
Colombo averages roughly 300 to 380 mm of rain in May, often the most of any month. Galle and the south coast are similar. Rain comes in heavy bursts with sunny spells in between rather than as constant drizzle, but some days are wet from morning to night, especially at the onset.
The sea is the biggest change. From late May, swell and strong currents arrive on beaches from Negombo to Tangalle, and many fly red flags. Whale-watching from Mirissa stops, and the south coast surf breaks become too big and messy for beginners.
Humidity stays high, but the wind and cloud keep temperatures slightly lower than in April, around 30 to 31 °C. Galle Fort, Colombo's museums and the south coast's temples work well in May; long beach days do not.
The hill country
The western slopes of the hills, including Nuwara Eliya, Hatton and the Adam's Peak area, catch the southwest monsoon as it rises over the mountains. Nuwara Eliya averages roughly 150 to 200 mm of rain in May, and the wind picks up from the onset. The Adam's Peak season ends at the Vesak full moon.
The eastern side of the hills is different. Ella, Bandarawela and Haputale sit partly in the rain shadow and are often drier and sunnier than Nuwara Eliya in May. Kandy gets afternoon storms and some monsoon rain, with highs around 30 °C.
The train between Kandy and Ella runs through both zones, and the views from it in May are often misty on the western section and clearer after Haputale.
- →Nuwara Eliya: roughly 150 to 200 mm, windy from late May.
- →Ella and Bandarawela: often drier and brighter.
- →Kandy: about 30 °C, afternoon showers.
The Cultural Triangle
The dry zone is hot in May, with highs around 33 to 34 °C at Sigiriya and Anuradhapura, and mostly dry. The southwest monsoon brings wind but little rain here. Early May can still bring an afternoon storm. Vesak, in May, lights up Anuradhapura and the temples of the region.
Climbs remain an early-morning activity. The steady wind from late May can be strong on the summit of Sigiriya and Pidurangala, but it also makes the heat easier to bear.
The east coast and the north
May is the start of the east coast's best season. Trincomalee averages only roughly 50 to 100 mm of rain, the sea at Nilaveli, Uppuveli and Pasikudah is calm and clear, and Pigeon Island snorkelling is reliable. Arugam Bay's surf season starts, with the southwest wind blowing offshore on the point breaks.
Highs on the east coast are about 33 °C, and the north is hotter. Jaffna is dry and windy, with highs around 33 to 34 °C. Whale-watching boats from Trincomalee begin running in some years from around May.
- →Trincomalee: roughly 50 to 100 mm, calm and clear.
- →Arugam Bay: surf season begins.
- →Jaffna: hot, dry and windy.
Planning around May weather
For a beach trip in May, the decision is simple: plan the beach for the east coast and the sightseeing for the Cultural Triangle and the eastern hills. The south and west coasts are still worth a visit for Galle and Colombo, but not for the sea.
May is a quieter, better-value month, and the rain on the southwest coast rarely lasts all day. Lankan Stays & Trails plans May routes through the Cultural Triangle, Kandy, Ella and the east coast, and keeps a day free on the southwest side for the weather.
Frequently asked questions
What is the weather like in Sri Lanka in May?
In May the southwest monsoon arrives on the west and south coasts and the western hills, usually in the second half of the month, with heavy rain and rough seas. The east coast and the north stay dry, hot and calm. The Cultural Triangle is hot, around 33 to 34 °C, and mostly dry.
Is May the wettest month in Colombo?
In many years, yes. Colombo averages roughly 300 to 380 mm of rain in May because the southwest monsoon sets in during the month. October is similar. The rain usually comes in heavy bursts with sunny spells in between, rather than all day, though onset days can be wet throughout.
Can you swim on the south coast of Sri Lanka in May?
Early in May, often yes. From the monsoon onset, usually in the second half of the month, the south and west coasts get strong swell and currents, and many beaches fly red flags. Swimming is not advised on those days. The east coast is calm and the safer choice.
When does the monsoon start in May in Sri Lanka?
The southwest monsoon usually reaches Sri Lanka in the second half of May, often in the third or fourth week, but the date varies by a week or two from year to year. Before onset, May weather is like April, with afternoon thunderstorms rather than steady monsoon rain.
Is May a good month for the east coast of Sri Lanka?
Yes. May is the start of the east coast's best season. Trincomalee averages roughly 50 to 100 mm of rain, the sea is calm and clear for swimming and snorkelling at Pigeon Island, and Arugam Bay's surf season begins as the southwest wind blows offshore.
Is it rainy in Ella in May?
Ella is often drier than the western hills in May because it sits partly in the rain shadow of the central mountains. Showers are possible, but many mornings are clear. Nuwara Eliya, on the western side, is wetter and windier once the southwest monsoon arrives.
How does Lankan Stays & Trails plan around the May monsoon?
May routes usually run through the Cultural Triangle, Kandy and Ella, then finish on the east coast at Trincomalee, Pasikudah or Arugam Bay, where the sea is calm. Galle or Colombo can still be included for sightseeing, with a flexible day for the weather.