For the plains, a “heat wave” is declared when the maximum temperature is more than 40 degrees Celsius, and at least 4.5 notches above normal.
A “severe” heat wave is declared if departure from normal temperature is more than 6.5 degrees Celsius, according to the India Meteorological Department (IMD).
“Usually, the capital witnesses heat waves till June 20. The increase in the maximum temperature this time can be attributed to the delay in the arrival of the monsoon,” Kuldeep Srivastava, the head of the IMD’s regional forecasting centre, said.
On Tuesday, Delhi witnessed the first severe heat wave of the year with the maximum temperature at Safdarjung Observatory, considered the official marker for the city, rising to 43 degrees Celsius, the highest this year so far.
Globally, the US states of Washington and Oregon, as well as British Columbia in Canada, boiled this week in all-time high temperatures that have caused dozens of deaths.
With inputs from NDTV