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Rainfall · Tamil Nadu

Rainfall in Chennai (Madras)

1,314 mmof rain in an average year, 2006–2025

Chennai gets 38% of its rain from the monsoon, June to September, and November is its wettest month. In 2025 it got 1,316 mm, 0% above average (normal).

Novemberwettest month, 323 mm on average
2015wettest year, 1,961 mm
2016driest year, 811 mm
8months a year with 50 mm of rain or more

Month-wise rainfall in Chennai

Average rain in each month, 2006–2025.

0100200300400JanJan: 24 mmFebFeb: 6 mmMarMar: 17 mmAprApr: 17 mmMayMay: 52 mmJunJun: 88 mmJulJul: 119 mmAugAug: 154 mmSepSep: 143 mmOctOct: 224 mmNovNov: 323 mmDecDec: 148 mm
MonthAverage rainShare of the year
January24 mm2%
February6 mm0%
March17 mm1%
April17 mm1%
May52 mm4%
June88 mm7%
July119 mm9%
August154 mm12%
September143 mm11%
October224 mm17%
November323 mm25%
December148 mm11%

Yearly rainfall in Chennai since 2006

Lighter bars are dry years, 20% or more below average (2012, 2013, 2016, 2018), when wells and borewells are drawn hardest.

010002000300020062006: 1,237 mm2007: 1,256 mm2008: 1,428 mm20092009: 1,165 mm2010: 1,362 mm2011: 1,371 mm20122012: 1,005 mm2013: 1,023 mm2014: 1,096 mm20152015: 1,961 mm2016: 811 mm2017: 1,290 mm20182018: 832 mm2019: 1,207 mm2020: 1,561 mm20212021: 1,841 mm2022: 1,364 mm2023: 1,526 mm20242024: 1,624 mm2025: 1,316 mm- - average 1,314 mm

What Chennai'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 Chennai sheds about 1,11,690 litres in an average year, most of it in a few wet 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 year2,23,380 L≈ 22 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.

Rainwater harvesting cost in ChennaiGroundwater level in ChennaiPonds and lakes in ChennaiWater quality in Chennai

Frequently asked questions

What is the average annual rainfall in Chennai?

About 1,314 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 2015 (1,961 mm) and the driest was 2016 (811 mm).

Which month gets the most rain in Chennai?

November, with 323 mm in an average year, followed by October and August. February is the driest month (6 mm).

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

38% of a normal year's rain falls from June to September. 8 months average 50 mm or more.

How much did it rain in Chennai in 2025?

1,316 mm, which is 0% above the 2006–2025 average, or "normal" in the India Meteorological Department's terms.

Is rainfall in Chennai increasing or decreasing?

It has held roughly steady: the last 10 years averaged within 5% of the 10 before them. Year-to-year swings are much bigger than the trend.

How much rainwater can a house in Chennai harvest?

A 100 m² (about 1,076 sq ft) concrete roof in Chennai sheds about 1,11,690 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 Chennai 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 Tamil Nadu