Mercury plummets 11.9°C in a day, caps off a hotter than normal June

There were 20 days in June when the city’s max temperature was above 40°C, hitting a peak of 44.2°C on June 5, showed Met data

NEW DELHI: Delhi ended June with an average monthly maximum temperature of 40 degrees Celsius – 0.8 degrees higher than the normal monthly average, largely owing to lack of rainfall as Delhi received 24.5mm of rainfall throughout the month -- a considerable deficit over the monthly normal mark of 65.5mm, an analysis of the India Meteorological Data (IMD) shows.

Thursday’s showers pushed the minimum temperature down by nearly 12 degrees Celsius (°C), not just stopping a punishing spell of stocky heat, but also giving Delhi its coolest day in 116 days.

There were 20 days in the month when the maximum temperature was more than 40 degrees, according to the data. The maximum temperature, however, dropped to 30.7 degrees on June 19, which was Delhi’s lowest maximum for the month since June 18, 2013, when it was recorded at 30 degrees Celsius.

Delhi’s average heat index (HI) or ‘real feel’ temperature, which takes into account humidity with the air temperature to calculate what the body actually feels, was 42.8 degrees Celsius. This means the city residents, on an average, felt much hotter than what the actual temperature was.

On June 28, the heat index in the city soared to 53 degrees whereas the day’s maximum temperature was 41.5 degrees.

The average wet-bulb temperature, another measure of how humidity impacts thermal discomfort and how easy or difficult it is to work outside, was recorded at 27.19 degrees. A wetbulb temperature of more than 29 degrees makes it uncomfortable to work outside in the open.

When it goes over 32 degrees, it is difficult for even fit and acclimatised people to work outside.

While Delhi received 116.6mm rain on June 30, it took place after 8.30 am on Thursday. This means that it will be accounted for in July’s rain data. The IMD calculates the day’s rainfall reading between 8.30am and 8.30am the next day. As a result, for June 30, Delhi only received ‘trace’ rainfall before 8.30am on Wednesday and 8.30am on Thursday.

Meanwhile rainfall from 8:30 am on Thursday until 8.30am on Friday will be taken as rainfall received in Delhi on July 1.

Similarly, for record-keeping purposes, Thursday’s maximum temperature, which is recorded at 5.30pm, is therefore accounted for in July data, with IMD’S record books ending the month with a maximum temperature of 40.9 degrees Celsius on Wednesday. This means Delhi’s average monthly maximum temperature, according to the IMD chart, was 40.4 degrees.

Thursday was the city’s coolest day this year since 28.2°C on March 6, around the time winter was on its way out.

“Delhi has only seen one active western disturbance throughout the month and there was no rainfall in the first two weeks, where temperatures consistently remained above 40 degrees,” said IMD scientist, RK Jenamani.

“Delhi then saw its only western disturbance between June 16 and 20, when temperatures dropped down to around 30.7 degrees too. However, we have now seen a return of rainfall only on the last day of the month,” Jenamani said, and added that this largely occurred after 8:30am and will not officially be part of June’s rainfall data.

Delhi has seen poor rainfall over the last four months. Delhi received zero monthly rainfall in March, as against a normal of 15.9mm, 0.3mm in April compared to normal of 12.2mm; 47.7mm rain compared to a monthly normal of 19.7mm in May, and recording a deficit again for June, which saw only six rainy days and primarily very light to light showers, shows IMD data.

On an average, July receives 210.6mm rainfall. Already, Delhi has recorded 116.6mm of rainfall for July. Last year, July recorded 507.1mm of rainfall in total – over two-and-a-half times the monthly normal.

Delhi saw only one active western disturbance in June and got no rainfall in the first two weeks of the month RK JENAMANI, IMD scientist