Number Theory: Why a minor deviation in April’s heat felt far hotter

India’s average maximum temperature for April was 35.83 degrees Celsius, 0.86 degrees higher than the 1981-2010 average, considered the normal, according to the gridded dataset of the India Meteorological Department (IMD). In IMD’s own analysis until April 28, maximum temperature was the fourth highest since 1901 and 1.12 degrees above normal. This difference in figures is because the gridded dataset uses a somewhat different list of stations and mathematical operations. Calculating the precise rank of April 2022 is also beside the point.

Temperature since March, and particularly in April, has demonstrated what even small deviations from normal can look like. The following four charts explain why that is the case.

1. Most regions don’t need a big deviation to get very hot in April

2. Even small deviations in the latter part of April can lead to high temperatures

3. India has seen very rapid warming post 1980s…

4. …and local factors made it worse this April