On April 16, the West Bengal administration released a directive instructing schools, colleges, educational establishments and universities, comprising private institutions, to stay shut the following week due to intense heat wave conditions. Additionally, it even advanced the summer vacations of some educational institutions.
This was a step in the right direction because according to the data from the IMD’s gridded database, in 2023, for the first time, the maximum temperature crossed the 40°C mark in Kolkata for the month of April. The oldest data available in the IMD gridded database was from April 1952.
On April 14, 16 and 17 of this year, the city’s maximum temperature crossed the mark, peaking at 40.4°C on April 14. These measurements are for the surface temperature at two metres above ground level.
Chart 1 |The chart plots the maximum temperatures recorded on the various days of April in Kolkata between 1952 and 2023. Each X mark corresponds to a maximum temperature recorded on a day in April. The higher the mark, the higher the maximum temperature
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As can be observed, only three marks crossed the 40°C point, and all are from 2023.
The analysis in 2023 is based on the information from the first 18 days of April. However, the data was compared to the entire month of April from earlier years. To put it differently, during the first 18 days of April 2023, Kolkata recorded maximum temperatures above 40°C on three different days. In contrast, none of the days of the month of April from the previous years, even when considering the full 30 days, crossed that mark. On April 23, 2016, the maximum temperature touched 40°C in the city but did not cross the mark.
This is of significance because temperatures increase gradually to peak at the end of April or at the start of May. Whereas in April 2023, the record temperatures were recorded around mid-April.
Chart 2 | The chart shows all the days between 1952 and 2023 that recorded a maximum temperature of 40°C or above in Kolkata. (Red cross) indicates April, (peach cross) indicates May and (blue cross) indicates June
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In previous years, the days that touched/crossed the 40°C mark came in May or June. This shows that warmer temperatures are being recorded much earlier this year.
West Bengal was not the only State to witness a warmer April. The Tripura administration declared on April 17 that all State-run and State-supported schools would be shut for six days starting April 18. A notice said that the decision was made in consideration of the students’ health. Following Tripura, Meghalaya announced the closure of all educational establishments in certain areas of the State due to a heatwave. This marks the first occurrence of such an event for Meghalaya. In Maharashtra, a gathering on April 16 that drew thousands of participants under the sweltering sun led to at least 13 persons succumbing to heat strokes.
Table 3 | The table lists the capital cities in India (I), the hottest day in April 2023 (II), and the maximum temperature recorded on that day (III), the hottest day for any April between 1952 and 2023 (IV), and the maximum temperature recorded on that day (V)
Apart from Kolkata, Thiruvananthapuram in Kerala, Aizawl in Mizoram and Imphal in Manipur also recorded their highest maximum temperature for the month of April this year.
The cities of Amaravati, Patna, Raipur, Gandhinagar, Ranchi, Bhopal, Jaipur, Hyderabad and Lucknow too crossed the 40°C maximum temperature mark on at least one day in April this year. But they did not cross the record set in previous Aprils.
rebecca.varghese@thehindu.co.in and vignesh.r@thehindu.co.in
Source: IMDLIB python library, which scrapes weather data from the India Meteorological Department. The libraray was developed for lwcc.in by Saswata Nandi, Pratiman Patel, & Sabyasachi Swain
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