Heatwaves persist but some areas remain cooler than average
The plight of Delhi and large parts of north-west and central India is in sharp contrast with large parts of the country, which were actually cooler than historical average in the second week of May.
On May 15, Delhi’s Mungeshpur automatic weather station recorded a maximum temperature of 49 degrees Celsius, perhaps the highest ever recorded temperature in the capital – these automatic weather stations only became operational this year so there is no past data for this locality. To be sure, temperatures were rising over the past week after a brief relief due to rain on May 5 and 7. The plight of Delhi and large parts of north-west and central India is in sharp contrast with large parts of the country, which were actually cooler than historical average in the second week of May. The biggest reason for this regional divergence in heat or lack of it is divergence in rainfall patterns. Here are six maps which explain this in detail.
India’s average maximum temperature in the week ending May 15 was lower than what it was in the last week of April
An HT analysis of India Meteorological Department’s (IMD) gridded dataset shows that India’s average maximum temperature in the week ending May 15 was 36.15 degrees Celsius. This number was 35.81 degrees Celsius in the period between May 1 and May 8 and 36.98 degrees Celsius in the last week of April. The scientific way to make temperature comparisons is to compare them with historical averages – it is the daily average of temperatures between 1981 to 2010.
Once this comparison is made, both the last week and the first eight days of May have actually been cooler than historic averages, unlike the last week of April.
But the national headline numbers hide the regional variation in intensity of heat
Was Delhi clocking its highest ever temperature in a week when the national average was lower than historic average the only aberration? Far from it. IMD’s gridded data shows an almost equal division of grids which experienced temperatures which were higher or lower than historic averages. Of the 301 grids in India’s gridded dataset map – a grid is the box between a longitude and latitude – 166 were hotter than historic normal while 134 were cooler than historic normal in the week ending May 15. This division was 193-107 in the period between May 1 and May 8.
Number of grids experiencing extreme temperatures increased in the week ending May 15
Just because a grid shows a maximum temperature which is higher than the historical average does not mean that it is in the grip of extreme heat. This is because the average temperature itself can be at pretty comfortable levels. This makes it important to track actual temperature levels to get an idea of the regions which actually faced extreme heat. In the week ending May 15, 22 grids had average maximum temperature of 45 degrees Celsius or above. There was no such grid in the period between May 1 and May 8. The number of grids which recorded average maximum temperature of 42.5 degrees and above increased from 29 in the period between May 1 and May 8 to 75 in the week ending May 15.