Hot weather persisted in many parts of India in April, and the highest temperatures yet could plague the country on Wednesday through the weekend.

A large majority of Indian households live in poverty and lack air conditioning, which increases people’s vulnerability to heat. The elderly are particularly exposed to high temperatures.

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The sky-high temperatures illustrate the overlap between natural variability and the effects of human-caused climate change, which are known to make heat waves more intense and prolonged.

Another heat wave on the way

Monday, many cities across the country recorded highs of over 109 degrees (42.8 Celsius); the city of Wardha in the mid-western state of Maharashtra soared to 113 degrees (45 degrees Celsius).

Temperatures are expected to rise further, jumping 10 to 15 degrees (5.5 to 8.3 degrees Celsius) above average in the second half of this week, reigniting concern among those with no way to escape the heat. Parts of northern and western India, especially areas near the borders with Pakistan and Nepal, could experience the most extreme heat. This is where highs can reach 110 to 115 degrees (44 to 46 Celsius) on Wednesday and Thursday.

Between Friday and Sunday, temperatures could soar as high as 120 degrees (49 degrees Celsius) if the most extreme forecast models are correct.

Temperatures could approach national records in India and Pakistan for the month of April. According to Maximiliano Herrera, an expert on global weather extremes, India’s highest reliable April temperature is 118.9 degrees (48.3 Celsius), set at Barmer in northwestern India in 1958. Nawabshah, Pakistan, about 125 miles inside the Arabian Sea, hit 122.4 degrees (50.2 Celsius) four years ago; this record, perhaps the highest temperature ever observed worldwide in April, may be more difficult to beat.

A contributor to the heat is the high pressure at mid-altitudes in the atmosphere, a dome-shaped “ridge” of descending air that eradicates cloud cover and deflects storm systems northward. This will allow the sun to freely penetrate, warming the previous dry air. Overall weather patterns suggest little relief in sight over the coming 10-day week, although the intensity of the heat may ease a bit next week.

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A summer spring in India

India’s average maximum temperature during the month of March was 91.6 degrees (33.1 degrees Celsius), narrowly surpassing the previous high of March 2010.

Fifteen Indian states and territories have been hit by heat waves since March, according to the Center for Science and the Environment, a research and public interest organization based in New Delhi. The states of Rajasthan and Madhya Pradesh in northwestern and central India have been hardest hit; each having observed 25 days of heat waves so far this spring.

At least one person died of heat-related causes in March in Maharashtra, while two others died after being struck by lightning.

In April alone, New Delhi, home to more than 25 million people, hit 100 degrees (37.7 degrees Celsius) 23 out of 25 days; the average high temperature is around 98 degrees (36.7 Celsius).

In total, the capital is running around 4.8 degrees (2.7 Celsius) above average for the month. Delhi posted a high of 107 degrees (41.7 degrees Celsius) for four days in April and reached 108 degrees (42.2 degrees Celsius) on April 19.

Potentially more problematic than high highs, however, were high overnight lows. This is especially true in the city, where the “urban heat island” effect stimulated by cement and paved surfaces traps thermal energy long after the sun has set. Nighttime hot lows prevent the body from having a nighttime cooling period, which increases heat stress and the propensity for negative health effects.

Delhi’s average nighttime low in April is 71 degrees (21.7 Celsius). Seven nights in April could not go below 75 degrees (23.9 Celsius).

Since early March, Delhi has received just 0.01 inches of rain. The average for March and April is 1.14 inches. Dryness enhances heat, because dry air is easier to warm, further sapping soil moisture and rooting the cycle.

Rainfall across the country was 71% lower for March 2022 than its long-term average. The IMD said rainfall over India was the third lowest since 1901.

Neighboring Pakistan recorded the world’s highest positive temperature anomaly during March, meaning the margin between observed temperatures and average temperatures was greater there than anywhere else in the world. Several stations set all-time monthly records in February and March.

Temperatures during this heat wave peaked at a dozen or more degrees above average.

Rising temperatures in India

In 2020, the IMD Ministry of Earth Sciences published a report citing a 1.3 degree (0.7 Celsius) increase in temperatures across India between 1901 and 2018.

In an extreme emissions scenario, he predicts that the frequency of summer heat waves will at least triple by the end of the century. He also warns that the frequency of hot nights is expected to increase by 70%.

Usually, temperatures begin to peak and decline sharply in late spring during the build-up of the summer monsoon, which occurs when onshore winds carry abundant moisture northward and bring very heavy downpours over a large part of the region. However, that too is changing.

“The overall decrease in seasonal summer monsoon rainfall over the past 6-7 decades has resulted in an increased propensity for droughts in India,” the ministry writes. It predicts “a high probability of increased frequency (>2 events per decade), intensity and extent of drought conditions in India” by the end of the century.

Jason Samenow and Kasha Patel contributed to this report.