Colombo Weather Guide: Climate, Monsoons & Seasons

Colombo sits just 7 degrees north of the equator, experiencing a tropical rainforest climate (Af) characterized by high humidity, consistent warmth, and significant rainfall. The city’s weather is dictated by the alternating rhythm of the Indian Ocean monsoons, which create distinct wet and dry phases rather than traditional four-season cycles.

Seasonal Weather Cycles

The Dry Season (December – February)

Often considered the most pleasant time of year, this period is influenced by the Northeast Monsoon. While this monsoon brings heavy rain to the east coast, Colombo—nestled on the west—is shielded by the central highlands.

• What to expect: Bright, sunny days and lower humidity compared to the rest of the year.
• Temperatures: Highs remain steady around 31°C (88°F), but nights are at their "coolest," occasionally dipping to 23°C (73°F).

First Inter-Monsoon (March – April)

As the Northeast Monsoon fades, the weather becomes "awkward" and transitional.

• What to expect: Wind speeds drop, and the air becomes stagnant and heavy. This is typically the hottest time of year, with sunlight peaking in March.
• The Feel: High humidity combined with peak temperatures makes the "real feel" significantly higher than the recorded 32°C (90°F). Afternoons often feature sudden, violent thunderstorms.

Southwest Monsoon (May – September)

Also known as the Yala season, this period brings the most significant rainfall to Colombo.

• What to expect: The monsoon arrives in two "pulses," peaking in May/June and again in September. Rainfall is often characterized by short, torrential downpours rather than day-long drizzles.
• Sea Conditions: The Indian Ocean becomes rough with high swells; red flags are common on beaches like Mount Lavinia.

Second Inter-Monsoon (October – November)

This phase is arguably the wettest and most unpredictable. Unlike the steady monsoon winds, this period is driven by atmospheric depressions.

• Weather Phenomena: This is the peak time for tropical cyclones in the Bay of Bengal, which can bring prolonged, heavy drenching to the entire island, including Colombo.

Daily Climate Behavior

In Colombo, the weather follows a predictable daily pulse. Mornings are usually clear and bright, even during the rainy seasons. As the land heats up, convective clouds build over the interior. By late afternoon or early evening, these clouds often drift back toward the coast, resulting in a "washout" that cools the city down for the night.

The "Feel" of Colombo

Humidity is the defining characteristic of Colombo's climate, rarely dropping below 70%. Locally, the weather is described as "sweaty" or "oppressive" during the inter-monsoon periods when the breeze dies down.

• Sea Breezes: The coastline offers a microclimate where the evening wind off the Indian Ocean provides immediate relief from the inland heat.
• Rainfall Adaptation: Locals are highly adapted to sudden floods. In many low-lying areas, life simply pauses for an hour during a downpour and resumes immediately once the water drains into the city's ancient colonial-era canal system.

Historical Context & Climate Trends

Historically, Colombo was built on a vast network of wetlands. Urban expansion has replaced many of these natural sponges with concrete, leading to increased localized flooding during peak monsoon months. While temperatures are stable, the intensity of the "inter-monsoon" thunderstorms has increased in recent decades, making the transitional months of April and October more volatile than in the past.