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Rainfall · Bihar

Rainfall in Arwal

1,010 mmof rain in an average year, 2006–2025

Arwal gets 84% of its rain from the monsoon, June to September, and July is its wettest month. In 2025 it got 1,381 mm, 37% above average (excess).

Julywettest month, 270 mm on average
2025wettest year, 1,381 mm
2022driest year, 632 mm
5months a year with 50 mm of rain or more

Month-wise rainfall in Arwal

Average rain in each month, 2006–2025.

0100200300JanJan: 11 mmFebFeb: 13 mmMarMar: 12 mmAprApr: 13 mmMayMay: 46 mmJunJun: 144 mmJulJul: 270 mmAugAug: 248 mmSepSep: 185 mmOctOct: 63 mmNovNov: 3 mmDecDec: 4 mm
MonthAverage rainShare of the year
January11 mm1%
February13 mm1%
March12 mm1%
April13 mm1%
May46 mm5%
June144 mm14%
July270 mm27%
August248 mm25%
September185 mm18%
October63 mm6%
November3 mm0%
December4 mm0%

Yearly rainfall in Arwal since 2006

Lighter bars are dry years, 20% or more below average (2009, 2010, 2018, 2022, 2023), when wells and borewells are drawn hardest. The last ten years averaged 5% less rain than the ten before.

05001000150020062006: 1,059 mm2007: 1,219 mm2008: 1,318 mm20092009: 767 mm2010: 739 mm2011: 1,082 mm20122012: 1,060 mm2013: 957 mm2014: 1,083 mm20152015: 1,070 mm2016: 1,179 mm2017: 861 mm20182018: 765 mm2019: 963 mm2020: 1,217 mm20212021: 1,249 mm2022: 632 mm2023: 707 mm20242024: 883 mm2025: 1,381 mm- - average 1,010 mm

What Arwal'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 Arwal sheds about 85,850 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?

Water you can put back each year1,71,700 L≈ 17 water tankers of 10,000 L

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 Arwal?

About 1,010 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 2025 (1,381 mm) and the driest was 2022 (632 mm).

Which month gets the most rain in Arwal?

July, with 270 mm in an average year, followed by August and September. November is the driest month (3 mm).

How much of Arwal's rain falls in the monsoon?

84% of a normal year's rain falls from June to September. 5 months average 50 mm or more.

How much did it rain in Arwal in 2025?

1,381 mm, which is 37% above the 2006–2025 average, or "excess" in the India Meteorological Department's terms.

Is rainfall in Arwal 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 Arwal harvest?

A 100 m² (about 1,076 sq ft) concrete roof in Arwal sheds about 85,850 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 Arwal district. It reads close to, but not exactly the same as, India Meteorological Department rain-gauge totals, and rain varies within a district.

Rainfall in other districts of Bihar