New Delhi: Delhi recorded its wettest May since 1901 as the city logged 185.9mm of rainfall, including two spells of heavy showers.The India Meteorological Department (IMD) has predicted an above-normal monsoon for the Delhi-Haryana-Chandigarh sub-division. An analysis of past data shows that the capital usually records two to three heavy rainy days during the monsoon, which inundate the city.When the southwest monsoon arrived in the city on June 28 last year, Delhi experienced a day of extremely heavy rain. Safdarjung, the city’s base station, logged 228.1mm. It was the highest rainfall recorded in a day in June since 1936. It brought the city to a halt, inundating almost all of Delhi, uprooting several trees, gridlocking traffic for hours, hampering flight movement following the collapse of the canopy at IGI Airport’s Terminal 1, disrupting power supply, and causing four deaths.However, the heavy rain continued during the monsoon. Safdarjung witnessed two more heavy-rain days in Aug 2024. Some parts of the city, including the Ridge and Pitampura, also recorded heavy showers in July last year.An analysis of IMD’s data for the monsoon period from June 1 to Sept 30 shows that seven heavy-rain days during the monsoon in 2021 was the highest in at least 60 years. Delhi saw two days of heavy rainfall in the monsoon of 2023 and just one such day in 2022. No heavy-rain days were seen in the monsoons of 2018 to 2020, but two such days each were reported in 2017 and 2015.Very heavy and extremely heavy rainy days are uncommon in Delhi. During the monsoons from 2011-2024, the capital saw just five very heavy rainy days and only one extremely heavy rainy day.Though IMD has not specified when the monsoon will arrive in the city, the Met department said that for Delhi, Chandigarh, and Haryana, a subdivision of the northwest region, the rainfall is expected to be greater than 114% of the long period average (LPA) in this monsoon season. “Delhi-Haryana-Chandigarh subdivision is likely to receive above-normal rainfall,” IMD director-general Mrutyunjay Mohapatra has said.The normal onset date of the southwest monsoon in Delhi is June 27. At present, its progression is ahead of the usual schedule. The monsoon arrived in Kerala on May 24, seven days earlier than its usual arrival of June 1. It reached Mumbai on May 26, ahead of its typical onset date of June 11. “We are monitoring the progress of the monsoon,” an official said.The capital received 1,029.9mm of rainfall last monsoon, which was 62% above the LPA of 640.4mm. In the monsoon season of 2023 and 2022, Delhi logged 660.8 and 516.9mm of rainfall, respectively. However, 2021 was the wettest monsoon since 1964, as Safdarjung logged 1,176.4mm of rainfall.According to the IMD, trace to 2.4 mm of rainfall recorded in 24 hours is considered very light rain, while light rainfall is between 2.5mm and 15.5mm.Rainfall recorded between 15.6mm and 64.4mm is categorised as moderate, while rainfall is considered heavy when it is from 64.5mm to 115.5mm. Rainfall logged between 115.6mm and 204.4mm is categorised as very heavy. When the rainfall of above 204.5 mm is called extremely heavy rainfall.During the pre-monsoon season from March 1 to May 30, Delhi received 103.8 mm of rain — nearly double the normal 55.5 mm — placing it in the ‘large excess’ category for the pre-monsoon period. The city, overall, received 87% excess rainfall in the pre-monsoon period.
