September Weather in Colombo Sri Lanka

Daily high temperatures are around 86°F, rarely falling below 84°F or exceeding 89°F.

Daily low temperatures are around 78°F, rarely falling below 76°F or exceeding 81°F.

For reference, on April 1, the hottest day of the year, temperatures in Colombo typically range from 78°F to 90°F, while on January 12, the coldest day of the year, they range from 74°F to 88°F.

The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on September. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Santa Marta, Colombia (10,266 miles away) and São Luís, Maranhão, Brazil (8,591 miles) are the far-away foreign places with temperatures most similar to Colombo (view comparison).

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The month of September in Colombo experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 81% throughout the month.

The clearest day of the month is September 25, with clear, mostly clear, or partly cloudy conditions 20% of the time.

For reference, on July 21, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 88%, while on March 4, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 44%.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Colombo, the chance of a wet day over the course of September is very rapidly increasing, starting the month at 35% and ending it at 52%.

For reference, the year's highest daily chance of a wet day is 70% on October 28, and its lowest chance is 19% on February 9.

Rainfall

To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during September in Colombo is very rapidly increasing, starting the month at 3.2 inches, when it rarely exceeds 6.4 inches or falls below 0.3 inches, and ending the month at 6.0 inches, when it rarely exceeds 10.4 inches or falls below 1.8 inches.

Over the course of September in Colombo, the length of the day is essentially constant. The shortest day of the month is September 30, with 12 hours, 4 minutes of daylight and the longest day is September 1, with 12 hours, 15 minutes of daylight.

The latest sunrise of the month in Colombo is 6:03 AM on September 1 and the earliest sunrise is 5 minutes earlier at 5:58 AM on September 30.

The latest sunset is 6:17 PM on September 1 and the earliest sunset is 15 minutes earlier at 6:02 PM on September 30.

Daylight saving time is not observed in Colombo during 2024.

For reference, on June 20, the longest day of the year, the Sun rises at 5:56 AM and sets 12 hours, 32 minutes later, at 6:28 PM, while on December 21, the shortest day of the year, it rises at 6:17 AM and sets 11 hours, 43 minutes later, at 6:00 PM.

The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation.

The figure below presents a compact representation of key lunar data for September 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The chance that a given day will be muggy in Colombo is essentially constant during September, remaining around 100% throughout.

For reference, on April 7, the muggiest day of the year, there are muggy conditions 100% of the time, while on January 28, the least muggy day of the year, there are muggy conditions 94% of the time.

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Colombo is decreasing during September, decreasing from 13.0 miles per hour to 11.6 miles per hour over the course of the month.

For reference, on June 9, the windiest day of the year, the daily average wind speed is 14.1 miles per hour, while on March 14, the calmest day of the year, the daily average wind speed is 5.9 miles per hour.

The hourly average wind direction in Colombo throughout September is predominantly from the west, with a peak proportion of 93% on September 1.

Colombo is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.

The average surface water temperature in Colombo is essentially constant during September, remaining around 82°F throughout.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

Temperatures in Colombo are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

The average accumulated growing degree days in Colombo are very rapidly increasing during September, increasing by 936°F, from 7,870°F to 8,806°F, over the course of the month.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy in Colombo is essentially constant during September, remaining within 0.1 kWh of 4.9 kWh throughout.

The highest average daily incident shortwave solar energy during September is 4.9 kWh on September 7.

For the purposes of this report, the geographical coordinates of Colombo are 6.932 deg latitude, 79.848 deg longitude, and 30 ft elevation.

The topography within 2 miles of Colombo contains only modest variations in elevation, with a maximum elevation change of 102 feet and an average elevation above sea level of 20 feet. Within 10 miles also contains only modest variations in elevation (226 feet). Within 50 miles contains only modest variations in elevation (7,175 feet).

The area within 2 miles of Colombo is covered by artificial surfaces (55%) and water (45%), within 10 miles by water (56%) and artificial surfaces (34%), and within 50 miles by water (59%) and trees (19%).