While temperatures cooled late this week even in northern India, if a person from north-western, western, or north-eastern regions of India were to look at India’s average weather in April, they would be surprised. This is because while these regions were suffering from heat waves in the month, it was a relatively pleasant summer for India on average. Most of this trend in temperatures has to do with rainfall, which was rare in north-west, west, and central regions but usual or more than usual elsewhere.

While temperatures cooled late this week even in northern India, if a person from north-western, western, or north-eastern regions of India were to look at India’s average weather in April, they would be surprised. This is because while these regions were suffering from heat waves in the month, it was a relatively pleasant summer for India on average. Most of this trend in temperatures has to do with rainfall, which was rare in north-west, west, and central regions but usual or more than usual elsewhere.

India’s average maximum temperature – this is the metric of relevance when looking at extreme heat in summer – in April was 35.11°C, according to the gridded dataset of the India Meteorological Department (IMD). This is ranked only 33rd warmest since 1951, the earliest year for which IMD has published gridded data. The average maximum in April was also only 0.15°C warmer than the 1981-2010 average, considered the normal for temperature.

While India’s average maximum was almost benign last month that is unlikely to have been the experience of people living in regions such as Punjab, Haryana, Delhi, western Uttar Pradesh, Rajasthan, Gujarat, eastern and northern Maharashtra, western Madhya Pradesh, and most of north-eastern India. While even usual temperatures in these regions (except north-eastern India) are relatively higher in April, they also experienced an upward deviation in maximum temperatures in the month. In most of Punjab, Haryana, Delhi, Rajasthan, Gujarat, and in parts of western Uttar Pradesh, maximum temperatures were at least 2°C warmer than normal. This is unlikely to be pleasant, because these regions are even usually the warmest places in the country in the summer season. To be sure, even Manipur and large parts of Assam experienced maximum temperatures warmer by a similar level, but these states do not get as warm in the summer as north-western and western India.

The reason behind this regional divergence in maximum temperature trends in April is rainfall. While most of the country has received rain, the regions that were warmer than normal were dry for most of the month. One reason for this is weaker western disturbances (storms originating west of India, usually in the mediterranean region), which bring rainfall to north-western India in April.

To be sure, north-eastern regions such as parts of Assam and Manipur were warmer than normal despite receiving more rain than north-western India. This is because they are even usually expected to be rainier than the rest of the country in April, but were less so this year. Therefore, it is the deficit in rainfall -- rather than rain in absolute terms – that has driven trends in maximum temperatures there.