It seems Mumbai has entered the summer season earlier than usual, with temperatures already touching heatwave levels in the first half of March. The city recorded its second heatwave in less than a week, an unusual development that has raised concerns about how intense the coming months could become. Meteorological data from several monitoring stations across the Mumbai Metropolitan Region painted a worrying picture with temperatures on an average shooting well above 40°C on an average. Even Byculla, typically moderated by its proximity to the coast, saw the mercury rise to 36.2°C. The coastal observatories reflected the same pattern of elevated temperatures. According to the India Meteorological Department (IMD), a heatwave is declared when the maximum temperature rises more than 6°C above normal levels. In some parts of the city, therefore, the threshold has already been crossed. Equally striking is how early this pattern has appeared. Mumbai experienced its first heatwave of the season last week when temperatures touched 38.9°C, making it the earliest such event in at least a decade. Within days, another intense spell has followed, suggesting that the region may be entering a longer and harsher summer than usual. The heat has not been confined to the city alone. The broader Mumbai Metropolitan Region, including Thane and Palghar districts, has also been affected. Pune, too, is experiencing temperatures above 35°C, well above what is typical for early March. Night-time temperatures have also been unusually high, adding to the discomfort. When nights fail to cool sufficiently, buildings and roads retain heat, making the following day feel even more oppressive. Meteorological explanations do not fully address the broader concern of extreme heat arriving earlier in the year. Over the past decade, India has experienced increasingly frequent and intense heatwaves, a pattern widely linked to rising global temperatures and rapid urbanisation. Cities such as Mumbai and Pune have been particularly vulnerable. Their expanding urban footprints, dense construction and declining green cover are creating ‘urban heat islands’ that trap warmth and amplify daytime temperatures. High humidity along the coast further worsens conditions by increasing the heat index - the measure of how hot it actually feels to the human body. The implications extend beyond weather statistics. Heatwaves affect labour productivity, strain electricity demand through air-conditioning use and increase the risk of heat-related illnesses. Outdoor workers - from construction labourers to delivery riders - are especially vulnerable, as are the elderly and those living in densely packed housing with little ventilation. Cities like Mumbai and Pune face a challenge that is no longer seasonal but structural. Urban planning must increasingly account for heat resilience: expanding tree cover, protecting wetlands that regulate local climates, designing buildings with passive cooling and ensuring access to shade and water in public spaces. The calendar still reads March. If the thermometer is already touching 40°C, the real test of the summer has not yet begun.
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