India’s INSAT-3DS satellite recorded a surge in evening crop burning in the days up to November 1, as the capital logged its first “very poor” reading of the season
Smoke from crop-residue fires in Punjab and Haryana drove Delhi’s air into the “very poor” category on Monday, according to an analysis of air-quality, weather and satellite data. Most of those fires were lit in the evening, hours after the NASA satellite that supplies the standard stubble-burning count had already passed over the region.
The capital’s air quality index (AQI) jumped from 117 on Saturday to 261 on Sunday. The Central Pollution Control Board’s 4pm bulletin on Monday recorded 324, the first very poor reading since February 11.
Weather alone cannot explain the spike. October 18 and 28 had equally calm nights and similarly strong temperature inversions, yet overnight PM2.5 averaged 68 and 127 µg/m³. On the night of November 1, it reached 194, more than three times India’s daily limit of 60.
Daytime readings point to pollution blowing in from outside the city. Afternoon heating usually disperses locally trapped pollution, and PM2.5 fell by nearly two-thirds on October 28. On November 1, it did not fall at all. Fine particles, which are typical of smoke, made up nearly 60% of particulate mass that night, compared with just over 40% on the comparison nights.
The satellite timing shows why the official count misses so much. NASA’s satellite crosses Punjab at about 1.30pm, but iFOREST data show that more than 90% of large fires in 2024 and 2025 began after 3pm. India’s geostationary INSAT-3DS, which watches the region all day, recorded evening fires rising from 17 on October 29 to 90 on November 1. North-westerly winds carried air across the fire belt toward Delhi.
High humidity may also have contributed. Meanwhile, NASA’s seasonal fire count is about a quarter lower than last year’s, a figure that reveals little now that farmers burn after dark.
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