Climate averages 1991–2020
Dehiwala-Mount Lavinia weather
in September.
A hot, very wet month: the joint 10th warmest and the 8th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a hot month in Dehiwala-Mount Lavinia: daytime highs average 28.2°C and nights cool to about 24.5°C. By daytime temperature it is the joint 10th warmest of the 12 months.
Expect about 232 mm of rain on roughly 24 days, which makes September a very wet month (the 8th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 10 min on an average September day.
The nearest other city in this atlas is Colombo (11 km away). In September its highs average 28.5°C, about as warm as Dehiwala-Mount Lavinia, with 223 mm of rain.
Among the 12 cities listed in Sri Lanka, Dehiwala-Mount Lavinia ranks joint 9th of 12 for the warmest September highs and 11th of 12 for the driest September (rainfall, lowest first). The mean September high of those 12 cities is 29.9°C; Dehiwala-Mount Lavinia is 1.7°C cooler than that mean.
From September to October, average highs rise by 0.3°C to 28.5°C, and monthly rainfall rises from 232 mm to 328 mm.
The annual picture
September in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Dehiwala-Mount Lavinia climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 29.9°C23.1°C | 23.1°C | 60 | 8.7 | 11.812 h |
| February | 30.8°C23.7°C | 23.7°C | 58 | 8.6 | 11.912 h |
| March | 31.0°C24.5°C | 24.5°C | 75 | 14.9 | 12.112 h |
| April | 30.4°C25.0°C | 25.0°C | 174 | 24.1 | 12.312 h |
| May | 29.2°C25.4°C | 25.4°C | 293 | 29.1 | 12.412 h |
| June | 28.6°C25.1°C | 25.1°C | 256 | 26.6 | 12.513 h |
| July | 28.2°C24.8°C | 24.8°C | 205 | 25.4 | 12.512 h |
| August | 28.1°C24.7°C | 24.7°C | 183 | 24.4 | 12.312 h |
| September, selected | 28.2°C24.5°C | 24.5°C | 232 | 24.3 | 12.212 h |
| October | 28.5°C24.2°C | 24.2°C | 328 | 26.1 | 12.012 h |
| November | 28.7°C23.7°C | 23.7°C | 330 | 23.8 | 11.812 h |
| December | 29.0°C23.3°C | 23.3°C | 174 | 16.5 | 11.712 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
September in nearby cities
- Colombo in SeptemberSri Lanka · 11 kmHigh 28.5°C · Low 24.5°C · 223 mm rain
- Negombo in SeptemberSri Lanka · 41 kmHigh 28.6°C · Low 24.9°C · 215 mm rain
- Galle in SeptemberSri Lanka · 96 kmHigh 27.7°C · Low 24.7°C · 240 mm rain
- Kandy in SeptemberSri Lanka · 98 kmHigh 27.1°C · Low 21.0°C · 121 mm rain
- Matara in SeptemberSri Lanka · 123 kmHigh 28.2°C · Low 24.6°C · 196 mm rain
- Ambalantota in SeptemberSri Lanka · 150 kmHigh 30.9°C · Low 25.1°C · 87 mm rain
- Batticaloa in SeptemberSri Lanka · 223 kmHigh 33.2°C · Low 25.6°C · 48 mm rain
- Kalmunai in SeptemberSri Lanka · 226 kmHigh 32.0°C · Low 25.9°C · 67 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Dehiwala-Mount Lavinia) is explained once on the Dehiwala-Mount Lavinia year overview and on the Sources, method and limits page.