One of the most-delayed and erratic monsoons in Delhi yielded 1,169.7 mm of rainfall, the third-highest since data has been maintained by the India Meteorological Department (IMD). Normally, Delhi records 653.6 mm of rainfall during the monsoon season. The rainfall this season was 80 per cent above normal. Last year, the capital gauged 576.5 mm of precipitation.
Three districts -- Central Delhi, New Delhi and North Delhi -- recorded large excess rainfall. Northwest Delhi and Southwest gauged excess rainfall. While west, south and east Delhi got ônormalö precipitation, only northeast Delhi recorded deficient rainfall.
According to the IMD, the Safdarjung Observatory, which is considered the official marker for the city, received 1,169.7 mm of rainfall this season. It had gauged 1,155.6 mm of rainfall in 1975 and 1,190.9 mm in 1964. The all-time record is 1,420.3 mm rainfall in 1933. This was the third time in the last two decades that the monsoon rainfall in Delhi breached the 1,000 mm mark. The city had recorded 1,031.5 mm of rainfall in the monsoon season in 2010. In 2003, the capital had gauged 1,050 mm rainfall.
Delhi received 636 mm, 544 mm, 876 mm, 370.8 mm and 505.5 mm rainfall during the monsoon season in 2011, 2012, 2013, 2014 and 2015, respectively. It recorded 524.7 mm of rainfall in 2016, 641.3 mm in 2017, 762.6 mm in 2018, 404.3 mm in 2019, and 576.5 mm in 2020, according to the IMD data.
September, in particular, was bountiful this season. The capital gauged 413.3mm of rainfall in the month, the highest after 417.3 mm precipitation recorded in September 1944 and the second-highest in 121 years. The September rainfall this year has been in marked contrast to last year, when the city got a meagre 20.9 mm precipitation in the month against a normal of 129.8 mm.
Despite the monsoon arriving in Delhi only on July 13, making it the most-delayed in 19 years, the capital recorded 16 rainy days in the month, the maximum in the last four years.
The string of rainy days brought 507.1 mm rainfall to the city, which was nearly 141 per cent above the long-period average of 210.6 mm. It was also the maximum rainfall in the month since July 2003, and the second highest ever.
The city recorded just 10 rainy days in August, the lowest in seven years, and a cumulative rainfall of 214.5 mm, lower than the average of 247 mm.
Delhi has also witnessed seven heavy rain events (64.5 mm to 115.5mm) this monsoon season so far, the highest ever, and these spells account for around 60 per cent of the rainfall recorded in the city. Six heavy rain days were recorded in the 1964 monsoon season.
Experts say the increase in the number of heavy rain events in many parts of the country is directly linked to climate change. Normally, Delhi records just one or two such events during the entire season, said senior IMD scientist R K Jenamani. The capital recorded three spells of heavy rain in July -- 69.6 mm on July 19, 100 mm on July 27, and 72 mm on July 30. While one heavy such episode occurred last month -- 138.8 mm of rainfall on August 21 -- Delhi has already witnessed three such events this month -- 112.1mm on September 1, 117.7 mm on September 2, and 94.7 mm September 11. The capital has been logging a new weather record every month since August last year.