Weekend rain gives city wettest Jan in 27 yrs, season’s lowest max temperature

The day saw the city receive 5.4mm of rainfall between 8.30am and 5.30pm, after 41mm rain the previous day, taking the total precipitation in Delhi for the month to 63.6mm -- the most in January since 1995.

The wettest January in Delhi for 27 years, the lowest daytime temperature so far this season and the cleanest air in over 80 days – a host of weather records tumbled in the national capital on a cold, wet, overcast Sunday.

At the Delhi-Gurugram expressway on Sunday. (PArveen Kumar/HT Photo)

The day saw the city receive 5.4mm of rainfall between 8.30am and 5.30pm, after 41mm rain the previous day, taking the total precipitation in Delhi for the month to 63.6mm -- the most in January since 1995, when the city received 69.8mm of rainfall in the entire month.

Delhi also saw the maximum temperature fall to just 15 degrees Celsius on Sunday – four below normal and the lowest so far this winter.

A rainy weekend also meant Delhi’s air stayed in the ‘satisfactory’ zone for a second straight day. The city’s 24-hour average air quality index (AQI) improved to 69, according to the Central Pollution Control Board’s (CPCB) daily 4pm bulletin, after Saturday’s reading of 91.

Till this weekend, Delhi had never seen a satisfactory air day in January, at least since CPCB started the AQI in 2015, making this spell even rarer.

This was also Delhi’s cleanest air day since October 19 last year, when the AQI was also 69.

The AQI in the Capital improved from 397 on Wednesday, to 258 on Thursday, 182 (Friday), 91 on Saturday, and then 69 on Sunday.

An AQI between zero and 50 is considered “good”, 51 and 100 “satisfactory”, 101 and 200 “moderate”, 201 and 300 “poor”, 301 and 400 “very poor”, and 401 and 500 “severe”.

Data from the India Meteorological Department (IMD) showed that Safdarjung, Delhi’s base station received 8.4mm of rainfall in the 24 hours till 8.30am on Sunday. In the next nine hours, the city added another 5.4mm of rain.

RK Jenamani, scientist at IMD, said a western disturbance brought Delhi over 50mm of rainfall in two days, and kept the city’s maximum and minimum temperature barely a degree apart for two consecutive days, an unusual occurrence.

While Delhi’s maximum and minimum on Sunday was 15 and 13.8 degrees Celsius respectively, it was 16.4 and 15.2 degrees respectively on Saturday – a difference of 1.2 degrees.

“This has been the most intense western disturbance so far this winter and while a majority of the rain usually occurs on one day, this time around, we have seen it spread out consistently over nearly two days. This has kept Delhi’s maximum and minimum almost together and there has been no difference between the night and day temperatures,” Jenamani said.

The last time Delhi had a lower maximum was on Wednesday, when similar conditions and rain led to a daytime temperature of just 15.7 degrees Celsius.

The IMD says the impact of the western disturbance over Delhi will abate by Sunday night, with moderate fog expected over the duration of next week.

While the maximum is expected to be around 17 degrees Celsius on Sunday, the minimum is forecast to drop to 9 degrees.

“This western disturbance has brought moisture, which will lead to moderate fog in the next few days. Isolated parts may even record dense fog. The minimum is also expected to start dropping once again and could touch 6 degrees Celsius by January 14,” Jenamani added.

City’s air quality may get worse from today: Safar

In terms of air quality, Delhi’s pollution levels are expected to start rising from Monday onwards, with a further drop in wind speed forecast for Tuesday and Wednesday.

“The AQI has improved further due to Saturday’s rain causing wet deposition of particulate matter, while Sunday’s rain spells with relatively high winds are likely to continue causing further improvement of air quality. From Monday onwards, air pollutants will gradually start to get accumulated in the air in the absence of rainfall and relatively moderate ventilation,” said the System of Air Quality and Weather Forecasting and Research (Safar), a government forecasting body.