NEW DELHI: Starting May 13, Delhi’s main weather station Safdarjung has logged temperatures of 40 degrees C and more every single day. That’s 39 days and counting, making this the longest spell of high heat in the capital in records of the past 74 years. It is also the severest heat spell in these years, with day and night temperatures among the highest ever recorded and as many as seven days when the mercury crossed 45 degrees.
TOI analysed IMD’s daily temperature logs at Safdarjung since 1951 and found that the longest streak of 40+ temperatures prior to 2024 was 32 days, recorded from May 9 to June 10, 1978 (including both days), followed by 27 days in 1984 (from May 13 to June 8), which can be extended to 34 days if a single day of below 40 degrees C temperature is disregarded. Another notable streak of extreme heat was in 1998, which extended to 27 days with a single day of below 40-degree C temperature.
El Nino, monsoon lull reasons for streakAs per these records, not only has the current heat spell extended far beyond any other in the past, Delhiites have also had to endure more temperature extremes than during any other spell. Day temperatures hit a peak of 46.8 degrees Celsius on May 29, the second highest maximum ever recorded at Safdarjung, next to only 47.2 degrees C logged on May 29, 1944. The only other long heat spell where the highest maximum came close was the one in 1998, when temperatures peaked at 46.5 degrees Celsius.
No other spell had as many as seven days when the maximum was 45 degrees Celsius or higher. Again, the 1998 spell was a distant second with four such days.
There have been as many as 12 heatwave days during the current spell, five in May and seven so far in June. This data is also likely to be highest although strict comparisons could not be made because the normal temperatures in the previous periods weren’t available. As per IMD’s categorisation, a heatwave day is when the maximum temperature is either 45 degrees C or more, or when it is more than 40 degrees Celsius and at least 4.5 degrees Celsius higher than normal.
Besides, the current streak has had six straight days of ‘warm night’ conditions (when the maximum is over 40 degrees Celsius and the minimum is at least 4.5 notches above normal). The highest maximum temperature was recorded at 35.2 degrees on June 19, the highest minimum in the capital since 1964.
So what led to this unprecedentedly long and severe spell of heat in the region this year? Said IMD chief Mrutyunjay Mohapatra, “Three-four factors combined to make it a summer of extremes this year. First, this is the year after an El Nino event, when summers are usually harsh in India. Second, there were no western disturbances impacting northern India from mid-May till June 18. This meant there was no rainfall for over a month in the region, leading to an accumulation of heat which was exacerbated by the presence of anti-cyclonic circulations. Third, the monsoon went into a lull. It has started moving again but hasn’t entered northwest India yet. These factors together led to the temperature extremes during the past month or so.”