After rain reduces, Mumbai faces heat; pollution levels rise

Over the past two days, the city witnessed hot and sultry conditions in the absence of rain since the beginning of the month. On Saturday, a thin layer of smog across

Over the past two days, the city witnessed hot and sultry conditions in the absence of rain since the beginning of the month. On Saturday, a thin layer of smog across the city skyline indicated a rise in pollution with a sepia-coloured sky during sunset.

HT Image

The city and suburbs witnessed recurrent flashes of lightning and loud claps of thunder between 1.30am and 3am on early Saturday morning.

The India Meteorological Department (IMD) predicted the possibility of thunderstorms in the evening or late night for Saturday and Sunday.

On Saturday, the maximum temperature in the suburbs was 33.6 degree Celsius, 2.5 degrees above normal, while it was 33.8 degree Celsius on Friday. In south Mumbai, the maximum temperature on Saturday was 33.2 degree Celsius, more than 2 degrees above normal. Humidity level was 90% during the day which dropped to 85% by the evening.

The pollutant-measuring indicator — air quality index (AQI) for PM2.5 pollutant or particles that can easily enter the lungs and cause ailments — was 78 which falls under ‘satisfactory’ category (51-100). This was the first time this monsoon that AQI was in that category as the levels had been below 50 throughout Covid-19 lockdown between March 21 and May 31 followed by monsoon onset on June 14. However, during the unlock phases there were isolated days when AQI was recorded in ‘satisfactory’ level. Saturday’s AQI was collated from all 10 locations where System of Air Quality Weather Forecasting and Research (SAFAR) monitors air quality.

SAFAR categorises AQI levels for PM2.5 in the 0-50 range as good; 51-100 as satisfactory; 101-200 as moderate; 201-300 as poor; 301-400 as very poor and above 400 as severe. An AQI of 73 (satisfactory) has been predicted for Sunday.

Researchers said drop in rain activity, increase in vehicular pollution and low wind speed led to higher pollution.

Meanwhile, rumbling thunder on early Saturday morning sounded like mini explosions, citizens said on social media adding that they were awakened by the weather activity. However, there was hardly any overnight rain. Between 11.30pm and 8.30am, the suburbs recorded 6.9mm rain while 15mm was recorded in south Mumbai. No rain was recorded on Saturday.

“On early Saturday morning, radar images showed very intense echoes over Alibag that slowly moved over Mumbai leading to thunder and lightning with light drizzling, but it faded soon. Similar weather is expected on Saturday and Sunday night or Monday early morning,” said KS Hosalikar, deputy director general, western region, IMD.

After record-breaking rain in July and August, September began with a break in rain activity with less than 20mm rain over the first five days. “Hot and sultry conditions combined with land heating during the day are allowing tall cloud formation by evening or late night. Rain activity is likely to be subdued over the next week for Mumbai,” said Hosalikar.