Thunderstorm cools Delhi, improves AQI, but hits flights

NEW DELHI: A thunderstorm triggered by a western disturbance swept across Delhi late on Sunday night, bringing strong winds and scattered rain that disrupted flight operations but sharply improved air quality and weather conditions.

Wind speeds touched up to 70 kmph between 11.30 pm and 12.30 am, forcing the diversion of 24 flights from Indira Gandhi International Airport. The storm brought a marked drop in temperatures, with the maximum at Safdarjung, the city’s base station, settling at 32.2 degrees Celsius — seven degrees below normal — providing relief after days of heat.

India Meteorological Department (IMD) issued a red alert for most parts of the city till 1.30 am, while a separate orange alert was sounded for southeast Delhi. Strong winds preceded brief spells of rain, which continued into the morning hours.

IMD has forecast more rain late on Monday night and in the early hours of Tuesday, with thundery activity likely on Wednesday. Temperatures are expected to rise again towards the weekend.

The storm also led to a sharp improvement in air quality, with the Air Quality Index (AQI) dropping to 88, placing it in the 'satisfactory' category. This was among the cleanest air days since Oct 8 last year, when the AQI stood at 80, and the best reading for May in three years. A day earlier, the AQI was 175, categorised as 'moderate'.

Following the improvement, the Commission for Air Quality Management (CAQM) lifted Stage 1 measures of the Graded Response Action Plan (GRAP), which has been in force since April 16. “The AQI of Delhi has shown significant improvement owing to rain and favourable meteorological conditions. Further, the forecast by IMD and IITM indicates that the AQI is likely to remain between 'satisfactory' and 'moderate' in the coming days,” CAQM said. Stage 1 includes preventive steps such as water sprinkling and anti-pollution drives, without imposing curbs.

Meteorologists attributed the sudden change in weather to a cyclonic circulation over Rajasthan moving south of Delhi.

“As is typical of pre-monsoon activity, rain is expected late at night or in the early hours, with sunshine returning by noon,” said Mahesh Palawat of Skymet. Cooler nights are likely to persist briefly before temperatures climb later this week.

According to IMD, the maximum temperature is expected to hover between 32 degrees Celsius and 34 degrees Celsius on Tuesday and rise to 35 degrees Celsius-37 degrees Celsius on Wednesday, touching around 40 degrees Celsius by Saturday as dry conditions return. The minimum temperature, which stood at 18.8 degrees Celsius — six degrees below normal — is likely to range between 18 degrees Celsius and 20 degrees Celsius on Tuesday, rising gradually to 23 degrees Celsius-26 degrees Celsius by the weekend.


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