New Delhi witnessed a month of contrasting weather extremes in May, recording its hottest May in two years while simultaneously achieving its cleanest air quality for the month in approximately five years, according to data from the India Meteorological Department (IMD) and other agencies.
Temperature Extremes
The city's average maximum temperature for 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 were 41.7 degrees Celsius and 26.5 degrees Celsius, respectively. The capital experienced fluctuating weather patterns throughout the month. Experts attributed frequent western disturbances and associated weather systems to early pre-monsoon activity, which kept 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.
Heatwave and Warm Nights
Mahesh Palawat of Skymet Weather, as cited by PTI, explained that the month's volatile weather resulted from a combination of western disturbances and induced cyclonic circulations over Rajasthan and adjoining areas, along with moisture-laden winds from the Bay of Bengal. Heatwave conditions were reported between May 18 and 21, with maximum temperatures exceeding 46 degrees Celsius in some parts of the city. Delhi also experienced 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 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.
Rainfall and Air Quality Improvement
Delhi received 17.61 mm of rainfall during the month. Palawat noted 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 contributed to improved 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) revealed that the capital's average Air Quality Index (AQI) was 161 until May 29, the lowest for the month since 2021, when it stood at 144. Experts highlighted that rainfall and intermittent strong winds played a crucial role in dispersing pollutants. While dust transported from Rajasthan triggered several dust storm events and affected air quality, localized intense rainfall helped wash out particulate matter and improve overall air quality across the city.
Air Quality Data
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, marking the cleanest air quality day in May since 2023 and the fourth satisfactory air quality day this month.
Outlook for June
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.
