A thunderstorm hit the city on Monday, lowering temperatures. Beginning with a drizzle around 8.30pm, the city experienced scattered rainfall, thunder and lighting for an hour.

However, the rain did not have a significant impact on the city’s air quality, which fell from 317 to 308 on the Central Pollution Control Board’s air quality index (AQI), almost five times the national safe limit of 60ug/m3.

Officials said that this recent spike in pollutants has been prevalent since May 8, when Western Disturbances began blowing in the direction of the National Capital Region from Rajasthan and parts of northern Gujarat.

The cyclonic circulation induced by these Western Disturbances might also bring scattered rainfall in parts of Haryana, Delhi, Uttar Pradesh and Punjab.

“We have been seeing increasing particulate matter across the NCR since May 8 due to high-speed and dust-raising winds. These are not only causing re-suspension of locally present dust, but also bringing in dust from neighbouring states,” a scientist with the CPCB’s air quality lab in Delhi said.

Monday’s AQI, however, marked an improvement from Sunday, when pollution levels touched 369 on the air quality index, with an average PM2.5 concentration of 369ug/m3—more than six times the safe limit.

According to the Early Air Quality Warning System for Delhi-NCR, air quality is set to deteriorate further over the next two days, with wind speeds of up to 14kmph expected on Tuesday, and up to 40kmph expected on Wednesday. Partly cloudy skies, dust storms and thunderstorms are also to be expected.

The Western Disturbances, however, have heldped lower the temperatures in the city, which have been lower than usual, said an official from the India Meteorological Department.

Maximum temperatures dipped slightly from 40°C on Sunday to 39.6°C on Monday. They are predicted to fall further in the event of rain, to about 38°C on Tuesday and Wednesday. Minimum temperatures will continue to remain in the 27°C-28°C range.

On May 8, the CPCB’s air pollution task force convened after almost five months to take stock of the situation. According to the minutes of the meeting, the task force “concluded that it is primarily dust from outside and localized sources contributing to rise in pollution levels in Delhi-NCR”. CPCB officials confirmed that the task force is monitoring the situation and would convene again this week if pollution levels continue to veer towards the ‘severe’ category.

First Published: May 14, 2019 03:34 IST