Dehiwala Monthly Rainfall & Precipitation
This page shows both the average monthly rainfall and the number of rainy days in Dehiwala, Colombo District, Sri Lanka. Long-term data from 1990 to 2020 was used to calculate these averages. Now, let's break down all the details for a clearer picture.
Dehiwala experiences significant rainfall throughout the year, averaging 2638 mm (104 in) of precipitation annually.
Monthly Precipitation Levels
The average number of days each month with precipitation (> 0.2 mm (0.01 in))
The climate in Dehiwala shows significant variation throughout the year. Expect 355 mm (14 in) of precipitation during the wettest month October, distributed over 16 rainy days.
In contrast, January offers drier and sunnier days, with around 74 mm (2.9 in) of rainfall over 5 rainy days.
October, the wettest month, has a maximum daytime temperature of 30°C (86°F). The city receives 202 hours of sunshine in this period. During the driest month January you can expect a temperature of 32°C (90°F). For more detailed insights into the city's temperatures, visit our Dehiwala Temperature page.
Daily Historical Precipitation
45-year average (1976-2025)
Average daily rainfall for each day of the month based on long-term records.
Average precipitation in July
Explore Dehiwala's Historical Precipitation: 1976-2026
Browse day-by-day precipitation records for Dehiwala spanning 51 years. Select any month and year to see actual rainfall and snowfall recorded on each day.
Annual Rainfall in Sri Lanka: City Comparison
The map below shows the annual precipitation across Sri Lanka. You can also select the different months in case you are interested in a specific month.
heavy rainfall
high
moderate
low
almost none
Dehiwala vs World: Rainfall Compared
Dehiwala's average annual precipitation is 2638 mm (104 in). Let's compare this to some popular worldwide tourist destinations:
In Barcelona, Spain, the average annual precipitation is 644 mm (25 in), evenly distributed across the year with no extreme wet or dry seasons.
In Seoul, South Korea, the average annual precipitation is 1237 mm (49 in), with most rain falling during the summer monsoon season.
In Tokyo, Japan, the average annual precipitation is 1528 mm (60 in), with significant summer rains due to typhoon season.
Singapore, situated near the equator, gets 2581 mm (102 in) of rainfall annually, with no distinct dry season and consistent monthly precipitation.
Precipitation amounts are measured using specific gauges installed at weather stations, collecting both rain and snow and any other type of precipitation. Rainfall is measured directly in millimeters, while that from snow and ice is obtained by melting it. Automated systems often incorporate heaters to make this easier.
Information from these stations is transmitted via Wi-Fi, satellite, GPS, or telephone connections to central monitoring networks. This information is immediately updated and integrated into weather models and forecasts.
Precipitation has a very strong role in determining the local climate and ecosystem:
- Changing Rainfall Patterns: Global warming causes drastic changes in the patterns of rainfall. Some areas have been experiencing increased frequency and intensity of rainfall, while other areas experience longer dry spells or even droughts.
- Local Impacts: Many regions are experiencing heavier rainfall in the winter months and drier, hotter summers. This affects agriculture, water resources, and ecosystems.
- The U.S. has a significant number of thunderstorms every year, with over 14.6 million taking place across the world annually.
- Approximately 70% of lightning bolts strike land rather than oceans.
- A storm named John was the longest-lasting Pacific tropical storm, continuing for 31 days. As it crossed the dateline twice, it changed status from a hurricane to a typhoon and back to a hurricane.
For more detailed information about Dehiwala's weather, including sunshine hours, humidity levels, and temperature data, visit our Dehiwala Climate page.
