Just two weeks after Mumbai endured a record-breaking heatwave, the India Meteorological Department (IMD) issued a fresh heatwave alert on Thursday for parts of Mumbai and neighboring districts of Thane and Raigad. The alert is in place from March 9 to March 11, with temperatures expected to exceed 38 degrees Celsius over the weekend, reported Times of India.
Although IMD scientists note that Mumbai is still transitioning into summer, the rising temperatures indicate a significant deviation from normal. On Friday afternoon, the city's two key IMD observatories—Santacruz and Colaba—recorded maximum temperatures close to 35 degrees Celsius. In Mumbai, a heatwave warning is triggered when temperatures surpass 37 degrees Celsius, or rise 4-5 degrees above normal, for at least two consecutive days. The season’s first heatwave alert was issued last month when temperatures exceeded 37 degrees Celsius for four straight days.
Why is Mumbai's temperature rising by 4-5 degrees?
Meteorologists attribute the expected temperature spike to an anticyclone system forming over the region. IMD Mumbai scientist Nitha Sasidharan explained that this system will bring strong easterly winds from the interior parts of the country, delaying the arrival of the sea breeze. "Since these easterlies are strong, they will delay the westerly winds, i.e., the sea breeze, from setting in. Owing to this, the city can expect a spike of over 4-5 degrees Celsius above the normal from Sunday,” Sasidharan said.
Such fluctuations in March are not unusual for Mumbai. IMD data shows that the city recorded a maximum temperature of 38.8 degrees Celsius in March 2024, while in previous years, temperatures peaked at 39.4 degrees in 2023, 39.6 degrees in 2022, and 40.9 degrees in 2021.
Why are heatwaves becoming more frequent in Mumbai?
A study of meteorological data from IMD Santacruz, included in the Mumbai Climate Action Plan (2022), found that between 1973 and 2020, the city experienced 12 heatwave events. Over the last 47 years, Mumbai has shown a warming trend, with temperatures rising by 0.25 degrees Celsius per decade.
According to projections by the National Oceanic and Atmospheric Administration (NOAA) and Climate Lab, by 2040, high-heat days—when the maximum temperature exceeds 32 degrees Celsius—will make up 60% of the year in Mumbai.
Mahesh Palawat, vice president of meteorology and climate change at Skymet Weather, said shifting wind patterns are a common cause of heatwaves, but their frequency has increased due to climate change. "Typically, heatwaves are a result of the change in wind directions, which are common during summers. However, there has certainly been an increasing trend in the number of heatwaves over the years. This is a result of global warming and climate change, whose impacts on global temperatures have become more visible in recent years," Palawat said. He added that rising greenhouse gas levels are contributing to higher air temperatures and reduced cold waves, even in northern India.
How to stay safe during a heatwave
Heatwaves, marked by prolonged periods of high temperatures and humidity, can pose serious health risks, including heatstroke and dehydration. While IMD's current ‘yellow’ alert suggests that temperatures are generally tolerable, vulnerable groups such as infants and those with chronic illnesses may be at higher risk.
Dr. Mohan Joshi, dean of Sion Hospital, emphasized the importance of staying hydrated and avoiding direct sunlight. "Besides avoiding the sun, people must drink water to ensure adequate hydration. Children and extremely old people should particularly avoid heat as it can cause heat strokes, viral fever, and even renal stones, which are caused due to dehydration," Joshi told The Indian Express.
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