Rainfall in Bongaigaon
Bongaigaon gets 65% of its rain from the monsoon, June to September, and June is its wettest month. In 2025 it got 1,856 mm, 10% below average (normal).
Month-wise rainfall in Bongaigaon
Average rain in each month, 2006–2025.
| Month | Average rain | Share of the year |
|---|---|---|
| January | 5 mm | 0% |
| February | 17 mm | 1% |
| March | 50 mm | 2% |
| April | 187 mm | 9% |
| May | 327 mm | 16% |
| June | 423 mm | 21% |
| July | 367 mm | 18% |
| August | 290 mm | 14% |
| September | 253 mm | 12% |
| October | 126 mm | 6% |
| November | 7 mm | 0% |
| December | 3 mm | 0% |
Yearly rainfall in Bongaigaon since 2006
Lighter bars are dry years, 20% or more below average (2006), when wells and borewells are drawn hardest. The last ten years averaged 10% more rain than the ten before.
What Bongaigaon's rain is worth to a building
Every millimetre of rain on a square metre of roof is a litre of water. A 100 m² roof in Bongaigaon sheds about 1,74,675 litres in an average year, most of it in four monsoon months. Sent into a recharge pit, it refills the ground instead of flooding the street.
Your building: how much can you recharge?
1 mm of rain on 1 m² is 1 litre. The surface factor allows for water lost to splash, evaporation and first-flush.
Frequently asked questions
What is the average annual rainfall in Bongaigaon?
About 2,055 mm a year, averaged over 2006–2025 from NASA POWER satellite and weather-model data for the centre of the district. The wettest year in that time was 2020 (2,775 mm) and the driest was 2006 (1,622 mm).
Which month gets the most rain in Bongaigaon?
June, with 423 mm in an average year, followed by July and May. December is the driest month (3 mm).
How much of Bongaigaon's rain falls in the monsoon?
65% of a normal year's rain falls from June to September. 8 months average 50 mm or more.
How much did it rain in Bongaigaon in 2025?
1,856 mm, which is 10% below the 2006–2025 average, or "normal" in the India Meteorological Department's terms.
Is rainfall in Bongaigaon increasing or decreasing?
The last 10 years averaged 10% more rain than the 10 before them. Year-to-year swings are still bigger than that change.
How much rainwater can a house in Bongaigaon harvest?
A 100 m² (about 1,076 sq ft) concrete roof in Bongaigaon sheds about 1,74,675 litres in an average year: area × rainfall × 0.85 for splash and evaporation. Sent into a recharge pit, that refills the ground under the house instead of running into the drain.
Rainfall from NASA POWER (bias-corrected satellite and weather-model rainfall) at the centre of Bongaigaon district. It reads close to, but not exactly the same as, India Meteorological Department rain-gauge totals, and rain varies within a district.