Historic end for India's monsoon season

Heavy monsoon rainfall in Jaipur in August left this car caked in mud.

(CNN)India's famous monsoon has come to an end, and for the second consecutive year, the country observed an "excess" rainy season.

The rainfall average across the nation reached 109% of normal. This falls one percentage point shy of 2019's historic season of 110% above normal, which was the wettest monsoon season since 1994.
This makes the first time back-to-back rainy seasons had this large of a rainfall surplus since the 1950s. 2019 and 2020 rank as the second and third wettest season's respectively since 1990.
    The India Meteorological Department classifies a monsoon as normal when total rainfall from June through September falls withing the range of 96-104% of average.
    Totals between 104-110% of normal are considered "excess," while anything above 110% is designated as "large excess." Since monsoon records began in 1988, only the seasons of 1988, 1994 and 2019 were wetter than 2020.

    A robust start

    This year's monsoon began June 1 -- exactly on time -- in the southwest Indian state of Kerala. Simultaneously, Tropical Cyclone Nisarga formed in the Arabian Sea, off India's west coast. It made landfall south of Mumbai days later and pushed tropical moisture into central India.
    The monsoon progressed quickly, and complete coverage of India by the monsoon happened on June 26 -- 12 days early.
    The month ended with an excess rainfall of 18%, marking the first time since 2017 that June ended with a surplus of rain.
    As the "wet season'" continued, the month of August ended with a large surplus at 27% above normal. This is the largest amount of rain to fall within that month in 44 years.

    Factors that led to the record August rainfall

    The north Bay of Bengal had a number of disturbances that funneled tropical moisture across the Indian Himalayan Region, which impacted six states. The heavy rain intensified river flooding across the region, causing landslides and killing dozens, and it prompted evacuations of thousands of residents.
    There was also enhanced moisture from the Arabian Sea into western India due to increased upper-level winds. This led to the devastating landslide that killed dozens in Kerala and helped add to the record rainfall Mumbai experienced.
    Mumbai observed nearly 3,700mm of rainfall since June 1, enough to catapult it into the second-wettest monsoon season on record, just short of the previous record set back in 1958.

    Despite surplus, a water crisis looms

    Normally, a monsoon surplus would be considered favorable for a country so dependent on its arrival. It brings an end to the extreme heat of India's dry season, where temperatures can hit 50 degrees Celsius (122 degrees Fahrenheit) in some areas.
    According to the National Institution for Transforming India, rain received from June through September makes up 70% of the country's annual rainfall, which irrigates crops and supplies drinking water.
      This helps support the economy of the second-most populous country in the world -- 17% of India's GDP comes from agriculture, which employs half of its workforce.
      Following five consecutive below-average seasons from 2014 to 2018, the surplus rainfall of 2019 and 2020 has helped replenish reservoirs. However, the country's population of over 1.3 billion still faces a long-term crisis as it heads toward outgrowing its water supply.
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