"Heat wave days, when counted for Safdarjung airport, city's base station, based on 5-days based Pented normal - the method IMD follows for heat wave and severe heat wave - for the month of April and corresponding actual maximum temperature observations for the last 12 years, i.e., 2011 to 2022, has shown that April 2017 had the longest heat wave with six days while the current month, April 2022 till Monday, April 11, has become the second highest with five days," IMD's senior scientist R.K. Jenamani said.

 

On Monday, Safdarjung recorded maximum temperature of 41.8 degrees Celsius against the normal of 36.3 degrees Celsius, six notches above normal, Palam recorded the maximum temperature of 41.8 against the normal of 38.8, a departure of 5, Lodi Road recorded 42 degrees Celsius against the normal of 36 degrees Celsius, a departure of 6, Ridge observatory recorded 43 degrees Celsius against the average of 36.1 degrees Celsius, a departure of 7 while the Aya Nagar station recorded 43.6 degrees Celsius against the normal of 36.8 degrees, also 7 notches above normal.

 

The criterion for declaring a heat wave by IMD is when maximum temperature for any station reaches at least 40 degrees Celsius or more for plains and at least 30 degrees Celsius or more for hilly regions. Also, when the departure from normal is 4.5 degrees Celsius to 6.4 degrees Celsius, it is declared as a heat wave while when the departure from normal is more than 6.4 degrees Celsius, it is declared as a severe heat wave.

 

Based on actual maximum temperatures, a station recording a maximum temperature of 45 degrees Celsius or more is declared as having a heat wave while the one that records 47 degrees Celsius or more is declared to have a severe heat wave.

 

Meanwhile, under the influence of a Western Disturbance, light/moderate, isolated/ scattered rainfall is likely over Western Himalayan region during April 12 to 15 with maximum intensity on April 13 and isolated rainfall is likely over Punjab and Haryana on April 13, IMD said, adding, there is no chances of rain but the WD may help bring some respite in the soaring temperatures in Delhi NCR.