September 2021 could be Delhi’s wettest month ever! Here’s why

Delhi Rains: The rainfall in Delhi largely remained dry and significantly low in July. This year, the monsoon season was more active than ever before with the national capital recording nearly 70 per cent of its monsoon season’s rainfall in just 10 days of September. On Saturday, Delhi recorded 1,100mm of rainfall this monsoon season. It was in 2003, when Delhi witnessed such record breaking showers with total rainfall of 1,050, during monsoon. In fact, an orange alert was issued by the Indian Meteorological Department in the national capital which predicted moderate to heavy rainfall as well as thunderstorms over Delhi NCR between 7 am and 10 am. Let us break it down further and understand what’s happening and why September could be the wettest month in Delhi.

Normal rainfall in Delhi between June-September
This monsoon season, Delhi received a mean rainfall of 55.3mm, which is 34 per cent of the rainfall which occurs in August. It is then followed by July contributing 311 per cent, September with 22 per cent and then June at 13 per cent. Delhi’s annual rainfall is recorded at 670.7mm out of which we have already received 553.8mm (about 83 per cent) during June to September period. The normal rainfall we witness in the month of June (when the monsoon arrived) is 62 to 64 mm and for August, it is between 182-200mm and September, it is about 115.6mm.
Rainfall Delhi recorded this year.

Delhi recorded 29.6mm and ended 54 per cent below normal in June this year . After the monsoon arrived, rainfall in July improved and the rainfall touched 338.8mm mark. August this year witnessed less rainfall comparatively given this month generally records season’s maximum rainfall. Delhi’s rainfall was recorded at 214.5mm last month at 14 per cent deficient

Why is this September exceptionally wet for Delhiites?
The September normal rainfall in Delhi is just 115.6mm but the 24 hours of rainfall recorded at Delhi, Safdarjung (at 112.1mm and 117.7mm) were exceptionally high at this time of the year. Delhi’s rainfall figures for this month have touched 386.5mm (as on Sep 13) due to the 10 rainy days out of the total 13 this month. Dr K Sathi Devi, head, National Weather Forecasting Centre, New Delhi said that rainfall is largely due to consecutive and persistent low pressure systems formed in the Bay of Bengal.

As per IMD’s report titled ‘Observed Rainfall Variability and Changes over Delhi State’ neither monsoon seasonal or annual rainfall have shown any significant increase or decrease in rainfall trend during the past 30 years which is between 1989 to 2018. The highest June rainfall of 146mm was recorded in 2008, July (456.2mm) in 2003, August (457.8mm) in 1995 and September (325.33mm) in 2010, in the last three decades. New Delhi and Central Delhi received the maximum rainfall during the monsoons. East and North West Delhi areas record the lowest.