How hot is it inside when there’s a heatwave outside?

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Editor's note: The honest answer to this question that I (and I assume, many of you) have is something like 25 degrees Celsius. That’s because most of us use air conditioners or devices like desert coolers to beat the heat. Some of us may even be living in houses whose roofs are not directly exposed to sunlight, or have trees and other vegetation nearby. So, what would the inside temperature be without an AC or a cooler? Without even a ceiling fan? With no ventilation? And a tin roof exposed to the sun? How about a house with a concrete roof located in a semi-arid region where water, electricity and tree cover are sparse? While we have impressive data on outside temperature (which is what the Met department and weather apps put out), there’s comparatively little more than anecdotal information on how this translates to the actual heat experienced inside different structures. This is a big gap since India—with its arid and tropical climate—is vulnerable to heatwaves and has already witnessed several deadly ones this year. Two research papers published last month …