Woollens out in Chandigarh as rain brings mercury down by 11 notches
Day temperature dropped from 29.5°C the day before to 18.5°C following just 1 mm rain; shallow fog to follow from Saturday night
After just 1 mm rain on Friday, the city’s maximum temperature plunged by 11 degrees, sliding from 29.5°C the day before to 18.5°C.
At 18.5°C, the day temperature was 10 degrees below normal for this time of the year and also lowest so far this season.
Before the rain started, the temperature was already 23.5°C, five degrees below normal, and dropped further to 18.5°C after noon as the rain spell began.
On the other hand, as clouds do not allow the heat of the earth to escape by night, the minimum temperature rose from 14°C to 16.2°C, 2.9 degrees above normal and highest since 17.1°C on October 23.
Wettest November since 2020
The meagre 1 mm rain was also highest in November since 2020, when 15.1 mm rain was recorded on November 16. Rain is likely to stop from Saturday onwards, as per the India Meteorological Department (IMD), when shallow fog will start forming due to the relatively high humidity and low temperature.
In 2022, only trace rain (less than 0.1 mm) was recorded in the city on two days in November. Trace rain is not counted towards the monthly total. Even in 2021, 0.6 mm rain was recorded in the whole month, just on November 3.
With just one day of rain, this November, as a whole, has already become the wettest since 2020, when 20.4 mm rain was recorded in the entire month.
As per IMD, November is the driest month of the year, with average rain of just 9.9 mm. Of all months, November also has the least number of rainy days in the city.
Speaking about Friday’s rain, IMD Chandigarh director Manmohan Singh said, “An active Western Disturbance (WD) led to the rain. But its effect will decrease from Saturday onwards and rain will remain unlikely now.”
Singh added that the WD had been keeping night temperature on the higher side, but it was likely to drop over the weekend.
Snowfall was also recorded in Himachal Pradesh, where the day temperature in Shimla dropped to 15.2°C. As per Singh, the snow will also bring in cold winds in the region and contribute towards fall in temperature in the coming days.
AQI remains poor even after rain
While the drizzle started around 11.30 am, it didn’t have an effect on the city’s air quality, which continued to worsen till night.
At 8 pm, the Air Quality Index (AQI) was the worst at the Continuous Ambient Air Quality Monitoring Station (CAAQMS) in Sector 53, with a reading of 258 that falls in the “poor” category (201-300).
The station in Sector 22 had a reading of 232 and that in Sector 25 — 215.
The air quality had first turned “poor” on Sunday, and after improving to “moderate” (101-200) on Monday and Tuesday, it has remained “poor” since Wednesday.
Panchkula continued to have cleaner air, with an AQI of 184 at the Haryana State Pollution Control Board in Sector 6, Panchkula, at 8 pm.
Explaining this, Singh said there was only a small spell of rain that had no effect on AQI. “Further, the day temperature after the rain, fell by over five degrees from before it started raining. This led to temperature inversion, which causes AQI to increase.” UT environment director TC Nautiyal was unavailable for a comment.
Air quality to worsen on Diwali
However, Friday’s rain can lead to the AQI increasing further on Diwali night. Speaking about this, Dr Ravindra Khaiwal, professor of environment health at PGIMER’s department of community medicine, said, “Because of the rain, the temperature will fall. This will decrease the atmospheric mixing layer of the region, which will make it harder to get rid of emissions for the next few days, including Diwali.”
Khaiwal added that the effect of the rain on the 24-hour average AQI will be visible after around 12 hours.