Scorching heat, cleaner air: Delhi’s May weather swings between extremes

NEW DELHI: Delhi witnessed a month of weather extremes in May, recording its hottest May in two years while also registering its cleanest air quality for the month in about five years.According to data, the city's average maximum temperature in May stood at 39.7 degrees Celsius, while the average minimum temperature was 25.8 degrees Celsius. The last hotter May was in 2024, when the average maximum and minimum temperatures reached 41.7 degrees Celsius and 26.5 degrees Celsius, respectively.The capital experienced changing weather patterns throughout the month. Experts said frequent western disturbances and associated weather systems led to early pre-monsoon activity, keeping temperatures lower during the first half of May.

As these systems weakened, temperatures rose sharply and heatwave conditions developed across parts of Delhi before another spell of strong pre-monsoon activity returned towards the end of the month.Mahesh Palawat of Skymet Weather, as cited by PTI, attributed the month's fluctuating weather to a combination of western disturbances and induced cyclonic circulations over Rajasthan and adjoining areas, and moisture-laden winds from the Bay of Bengal.

Heatwave conditions were reported between May 18 and 21, with maximum temperatures crossing 46 degrees Celsius in some parts of the city.Delhi also witnessed unusually warm nights, with minimum temperatures reaching 32.8 degrees Celsius on May 26 and 31.9 degrees Celsius on May 21, among the highest nighttime temperatures recorded in the city in the last 14 years, according to the India Meteorological Department (IMD).The IMD defines a heatwave as a situation where the maximum temperature exceeds 40 degrees Celsius and is 4.5 to 6.4 degrees Celsius above normal.A warm night is declared when the maximum temperature remains at 40 degrees Celsius or higher, and the minimum temperature is also 4.5 to 6.4 degrees Celsius above normal.Delhi received 17.61 mm of rainfall during the month. Palawat mentioned that thunderstorms, rain and gusty winds intensified during the latter part of May, bringing widespread weather activity across the capital and providing relief from the intense heat over the past few days.The rainfall and strong winds also helped improve air quality. Despite the high temperatures, Delhi recorded its cleanest May air quality in around five years.An analysis by the Centre for Research on Energy and Clean Air (CREA) showed that the capital's average AQI was 161 until May 29, the lowest for the month since 2021, when it stood at 144.Experts said rainfall and intermittent strong winds played an important role in dispersing pollutants.

While dust transported from Rajasthan triggered several dust storm events and affected air quality, localised intense rainfall helped wash out particulate matter and improve overall air quality across the city.Data showed that between May 1 and May 29, Delhi recorded three satisfactory days, 20 moderate days and six poor days, with no very poor or severe air quality days. In comparison, May 2021 recorded six satisfactory days, 22 moderate days and three poor days, with an average AQI of 144.

The average AQI stood at 170 in May 2025 and 223 in May 2024.On May 30, Delhi recorded a satisfactory AQI of 85 following widespread rainfall and strong winds. It was the cleanest air quality day in May since 2023 and the fourth satisfactory air quality day this month.Looking ahead, Palawat stated that no heatwave conditions are expected during the first week of June. However, temperatures are forecast to gradually rise from June 1 as the current spell of rain activity weakens and shifts away from the region.