Delhi received 74 mm of rainfall in 24 hours ending 8:30 am on Sunday, the second highest precipitation on a day in October since 2007, according to the India Meteorological Department data.
In 2021, the capital had logged 87.9 mm of rainfall on October 18.
The weather bureau said the ceaseless spell of rain brought down the difference between minimum temperature (20.8 degrees Celsius) on Friday and maximum temperature (23.4 degrees Celsius) on Saturday to 2.6 degrees Celsius -- the lowest since 1969.
Earlier, the lowest such margin was recorded on October 19, 1998 at 3.1 degree Celsius, the IMD added.
The incessant rain in the capital also yielded the second "good" air quality day of the year, with the 24-hour average air quality index settling at 48.
Delhi had recorded a 24-hour average AQI of 47 on September 16.
The neighbouring cities of Ghaziabad (14), Gurugram (32) and Greater Noida (23) also recorded 'good' air quality.
The Safdarjung Observatory, Delhi's primary weather station, recorded another 7.4 mm of rainfall between 8:30 am and 5:30 pm on Sunday.
The city recorded a minimum temperature of 19.3 degrees Celsius, a degree below normal, while the maximum temperature dropped 10 notches to settle at 24.1 degrees Celsius.
The current rains in Delhi are not monsoon showers, which had receded from the city on September 29 after giving 516.9 mm of rainfall against a normal of 653.6 mm, the IMD said.
According to the Met department, the interaction of a western disturbance, which lies as a trough in mid and upper air, with a deep trough of easterly wind at a lower level led to the post-monsoon rain in the Delhi-NCR region.
Mahesh Palawat, vice president (meteorology and climate change), Skymet Weather, said easterly winds brought moisture from the Bay of Bengal with a trough running from Andhra Pradesh to northwest Uttar Pradesh.
Easterly winds carried moisture from the Arabian Sea due to another trough extending from Delhi to east Rajasthan.
"In October to March, we get 3 to 5 such intense interactions," an IMD official said.
Palwat said these weather systems will weaken over the next two-three days.
Sporadic light to moderate rain is likely on Monday, but not much precipitation is expected the day after, he said.
The Palam observatory recorded 64.9 mm of rainfall in 24 hours ending 8:30 am. The Lodhi Road, Ridge, and Ayanagar weather stations received 87.2 mm, 60.1 mm, and 85.2 mm rainfall respectively, the IMD said.
Rainfall below 15 mm is considered "light", between 15 mm and 64.5 mm "moderate", between 64.5 mm and 115.5 mm "heavy", and between 115.6 mm and 204.4 mm "very heavy". Above 204.4 mm is considered "extremely heavy" rainfall.
