Rainfall in Supaul
Supaul gets 78% of its rain from the monsoon, June to September, and July is its wettest month. In 2025 it got 1,421 mm, 5% above average (normal).
Month-wise rainfall in Supaul
Average rain in each month, 2006–2025.
| Month | Average rain | Share of the year |
|---|---|---|
| January | 5 mm | 0% |
| February | 10 mm | 1% |
| March | 27 mm | 2% |
| April | 45 mm | 3% |
| May | 133 mm | 10% |
| June | 230 mm | 17% |
| July | 326 mm | 24% |
| August | 260 mm | 19% |
| September | 238 mm | 18% |
| October | 72 mm | 5% |
| November | 3 mm | 0% |
| December | 2 mm | 0% |
Yearly rainfall in Supaul since 2006
Lighter bars are dry years, 20% or more below average (2009, 2012, 2014, 2018), when wells and borewells are drawn hardest. The last ten years averaged 38% more rain than the ten before.
What Supaul'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 Supaul sheds about 1,14,835 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 Supaul?
About 1,351 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 (2,214 mm) and the driest was 2012 (923 mm).
Which month gets the most rain in Supaul?
July, with 326 mm in an average year, followed by August and September. December is the driest month (2 mm).
How much of Supaul's rain falls in the monsoon?
78% of a normal year's rain falls from June to September. 6 months average 50 mm or more.
How much did it rain in Supaul in 2025?
1,421 mm, which is 5% above the 2006–2025 average, or "normal" in the India Meteorological Department's terms.
Is rainfall in Supaul increasing or decreasing?
The last 10 years averaged 38% more rain than the 10 before them. Year-to-year swings are still bigger than that change.
How much rainwater can a house in Supaul harvest?
A 100 m² (about 1,076 sq ft) concrete roof in Supaul sheds about 1,14,835 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 Supaul district. It reads close to, but not exactly the same as, India Meteorological Department rain-gauge totals, and rain varies within a district.