Rainfall in Samastipur
Samastipur gets 83% of its rain from the monsoon, June to September, and July is its wettest month. In 2025 it got 1,043 mm, 6% below average (normal).
Month-wise rainfall in Samastipur
Average rain in each month, 2006–2025.
| Month | Average rain | Share of the year |
|---|---|---|
| January | 6 mm | 1% |
| February | 13 mm | 1% |
| March | 15 mm | 1% |
| April | 20 mm | 2% |
| May | 77 mm | 7% |
| June | 159 mm | 14% |
| July | 283 mm | 26% |
| August | 259 mm | 23% |
| September | 213 mm | 19% |
| October | 58 mm | 5% |
| November | 1 mm | 0% |
| December | 3 mm | 0% |
Yearly rainfall in Samastipur since 2006
Lighter bars are dry years, 20% or more below average (2009, 2010, 2018), when wells and borewells are drawn hardest. The last ten years averaged 5% less rain than the ten before.
What Samastipur'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 Samastipur sheds about 94,010 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 Samastipur?
About 1,106 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 2008 (1,716 mm) and the driest was 2018 (663 mm).
Which month gets the most rain in Samastipur?
July, with 283 mm in an average year, followed by August and September. November is the driest month (1 mm).
How much of Samastipur's rain falls in the monsoon?
83% of a normal year's rain falls from June to September. 6 months average 50 mm or more.
How much did it rain in Samastipur in 2025?
1,043 mm, which is 6% below the 2006–2025 average, or "normal" in the India Meteorological Department's terms.
Is rainfall in Samastipur increasing or decreasing?
The last 10 years averaged 5% less rain than the 10 before them. Year-to-year swings are still bigger than that change.
How much rainwater can a house in Samastipur harvest?
A 100 m² (about 1,076 sq ft) concrete roof in Samastipur sheds about 94,010 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 Samastipur district. It reads close to, but not exactly the same as, India Meteorological Department rain-gauge totals, and rain varies within a district.