Day temperatures in Kolkata in April rose by six degrees in the five years from 2019 to 2024 and the city experienced a maximum temperature of 40 degrees Celsius for nine consecutive days this year, according to a report by an environmental group.
The report — ‘Heatwave havoc in April, a month of record-breaking temperature’ — by SwitchON Foundation, a Kolkata-based non-governmental organisation, is based on the data collected from various sources, including the India Meteorological Department (IMD).
According to the report, similar to the rise in maximum temperature, the minimum temperature in April, too, has increased by 5 degrees over the same period. The report notes that in 2019, there were more frequent temperature fluctuations compared to 2024. Moreover, higher temperatures were observed in the final days of April in both years.
The report says that Kolkata experienced its highest-ever temperature in the past five decades on April 30 this year. The temperature reached 43 degrees Celsius, 7.4 degrees more than the normal temperature, indicating severe heatwave conditions in the city.
Additionally, the lowest minimum temperature of 24.7 degrees Celsius on April 12 was 0.9 degrees more than the normal temperature. The report states that the temperature in Alipur crossed 40 degrees Celsius for nine days in April of this year.
Based on the collected data, April 2024 had higher maximum temperatures on 90 per cent of days and higher minimum temperatures on 93 per cent of days compared to April 2019.
The report highlights the factors that have led to the increase in temperature in the West Bengal capital. Kolkata is currently experiencing a shortage of systems, such as cyclonic circulations or trough lines, that trigger rainfall in the city. Typically, moist air originating from the Bay of Bengal leads to rain, but this year, the air is lacking the required moisture due to the prevalence of dry winds, it says.
The report highlights studies conducted by universities in West Bengal that reveal that Kolkata’s annual mean land surface temperature has increased by 4.7 degrees in the last 30 years. This is primarily due to the city’s loss of vegetation and the subsequent increase in built-up spaces, which has led to the urban heat island effect.
According to the report, this year, April experienced the lowest amount of rainfall, except for April 7, when it rained only 0.5 mm in Kolkata. In comparison, last year, in April 2023, it rained on four occasions, accumulating 50 mm of rainfall. It is worth noting that three of these rainy days occurred towards the end of April.
SwitchON Foundation managing director Vinay Jaju said, “In the face of unprecedented heatwaves, it is imperative that we recognise the urgency of climate action and its profound impact on vulnerable communities. Let us unite to implement sustainable solutions that prioritise the well-being of all, ensuring a resilient future for generations to come.”
Kolkata recorded a maximum temperature of 34.2 degrees Celsius on Monday, with 90 per cent maximum humidity. The IMD has forecast thunderstorms, along with light to moderate rainfall, in the southern districts of the state on Tuesday. Starting Tuesday, all the districts are expected to experience light to moderate rainfall.