Delhi benefited from heavy rainfall this August due to a favourable weather system, even as the surrounding regions experienced a deficit, according to experts.A man rides a bicycle with an umbrella in hand amid rainfall in Delhi. (HT Photo)The capital recorded 354.1 mm of rainfall between August 1 and August 30 (until 5:30pm). This is over 100 mm higher than the India Meteorological Department’s (IMD) long-period average of 233.1 mm for the same period.The city last saw excess August rainfall in 2025 and 2024, when it recorded 400.81mm and 390.3mm rainfall, respectively — crossing the LPA for the first time since 2020, when rainfall was 237 mm.Since 2011, the city has crossed the threshold only six times: in 2026, 2025, 2024, 2020, 2013, and 2012.Also read: Delhi sees heaviest 24-hr rain in two years; residents cite waterlogging strainMonsoon axis keeps Delhi wetter than neighbouring statesAccording to weather experts, this year’s excess rainfall was due to the monsoon axis — the low air pressure that determines where it rains during the monsoon — which stayed over the city more than usual.“Rain depends on the weather systems formed over a region; however, this time the excess rain was primarily due to the surges of the monsoon axis. This year, despite the Haryana-Punjab-Rajasthan region seeing a rainfall deficit, Delhi saw excess rainfall because the monsoon axis stayed over Delhi-NCR and western Uttar Pradesh for longer than usual. Last year, there was a different pattern, and the entire north-western region, including Delhi, saw more rain. This year, the monsoon trough’s movement is more localised, and Delhi has been lucky,” stated amateur meteorologist, Navdeep Dahiya.Dahiya added that Haryana is currently experiencing an 18% rainfall deficit.Also read: Traffic police seek end to waterlogging at 26 spots in DelhiRain likely to return from SeptemberAccording to the IMD forecast, Delhi is likely to see a rainy start to September, with very light to light rain across the city on Tuesday, and multiple spells of light to moderate rain on Wednesday. For Thursday and Friday, IMD has forecast very light to light rain.“The upcoming two to three days are likely to be dry. From September 2, we see the monsoon trough moving towards us again. It is currently at the foothills of the Himalayas. We expect at least two rainy days from mid-week to the weekend. Thereafter, the rain is likely to subside for a few days,” explained Dahiya.August ends with moderate air qualityMeanwhile, Delhi’s average daily air quality index (AQI) was recorded at 129, in the “moderate” category. According to Central Pollution Control Board (CPCB) data, analysed by the Centre for Research on Energy and Clean Air (CREA), the city recorded a monthly average AQI of 95 in August this year, compared to a monthly average AQI of 89 last year.Also read: Delhi's August sees above-normal rain, warm nights and three-year-high AQINotably, the data includes AQI averages for the first 30 days of August this year, which included 11 days with “moderate” AQI, 19 days with “satisfactory” AQI, and zero days with “good” AQI.CPCB classifies AQI between 0 and 50 as “good”, between 51 and 100 as “satisfactory”, between 101 and 200 as “moderate”, between 201 and 300 as “poor”, between 301 and 400 as “very poor”, and over 400 as “severe”.