Delhi ended August with a monthly rainfall excess of 72%, and September is expected to start on an equally wet note, according to data and forecasts made by the India Meteorological Department (IMD)—it has already issued a yellow alert for Monday, predicting moderate showers across the city, with isolated pockets likely to receive heavy rainfall.
The IMD attributed the rainfall prediction to a combination of the monsoon trough and active weather systems, including a western disturbance. The IMD on Sunday also issued its monthly forecast for September, stating northwest India, including Delhi, is likely to record above “normal” rainfall in the month.
August ended with a monthly rainfall total of 400.1mm, which is 72% over the monthly long-period average (LPA) of 233.1mm. This is the wettest August since 2010, when Delhi logged 455.1mm of rainfall, according to the data.
Generally, going by past trends, September typically receives 123.5mm of rainfall, but logged excess rain last year, receiving nearly 200mm of rainfall. An excess this year is likely to push Delhi’s annual rainfall total beyond the 1,000mm mark.
“More rain is likely in northwest India. We will see consistent easterly winds which will continue to feed moisture. The monsoon trough is presently near Rajasthan and north Madhya Pradesh, while a western disturbance exists close to Pakistan and Punjab. We will see low-pressure areas forming in northern India, with significant spells of rain likely in the hills,” said Mahesh Palawat, vice president at Skymet.
Delhi crossed its annual rainfall mark of 774.4mm on August 14, marking the fastest such development since 2021, when the annual mark was breached on August 1. Delhi has already logged 963.4mm of rainfall this year, with more expected until September-end. The normal date for the withdrawal of the southwest monsoon from Delhi is September 25.
“We should cross this 1,000mm mark in September. Between September 1 and 3, we can expect decent rain in Delhi-NCR and consistent light rain after that, until September 7,” Palawat said.
The heaviest spell of rainfall in August was clocked on August 9, with 79mm logged in 24 hours. This was followed by a spell of 64mm on August 30.
The rain has also kept August cooler than usual. Overall, the average monthly maximum stood at 33.2 degrees Celsius (°C), making it the coolest August since 2012, when the average maximum was 33.1°C. The normal monthly average maximum is 34.2°C.
Nights, too, were cooler than usual, due to consistent rainfall and easterly winds. The average monthly minimum temperature was 25.1°C, 1.6°C below the monthly LPA and the lowest for Delhi in August in at least 14 years, according to IMD data.
“This is because we had consistent rainfall. We mostly had light to moderate spells of rain, but rain was recorded on 22 of the 31 days this August, meaning there was constant cloud cover and cooling due to winds and rain,” an IMD official said.
Excess rainfall has been recorded since May, which was the wettest May on record with 186.4mm of rainfall, over six times the normal average of 30.7mm. In June, Delhi recorded 107.1mm of monthly rainfall, an excess of 45% over the long-period average (LPA) of 74.1mm. In July, Delhi received 259.3mm of rainfall, which was 24% more than the LPA of 209.7mm.
The IMD, in its forecast for September, said that above-normal rainfall was likely across the country this month (over 109% of the LPA). “The monthly average maximum temperatures are also expected to remain normal to below normal in many regions of west-central, northwest and south India…” it said on Sunday.
Delhi recorded a maximum temperature of 32.1°C on Sunday, which was two degrees below normal. The minimum was 24.5°C, which was also two degrees below normal. The maximum is forecast to be around 30°C on Monday, with the minimum hovering around 23°C, it said.
Delhi’s air quality, meanwhile, was in the “satisfactory” range on Sunday. The overall air quality index (AQI) was 79 (satisfactory) at 4pm on Sunday, marginally higher than Saturday’s 4pm reading of 72 (satisfactory).