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As summer settles in across Japan, a familiar, almost deafening symphony fills the air. The lmain culprits? Cicadas, or “semi” (セミ). These tiny noisemakers orchestrate one of nature’s most grating soundtracks. But there’s more to their incessant racket than meets the ear—these relentless insects are finely tuned barometers, with their cacophonous chorus intensifying as temperatures rise.

Cicadas are the quintessential soundtrack of summer in Japan, especially in hot spots like Kagawa Prefecture. Male cicadas produce their racket using specialized structures called tymbals. The rapid buckling of these tymbals creates the clicking sound that, in chorus with thousands of others, forms the familiar summer drone. The rate of tymbal contraction and the intensity of the sound is directly influenced by temperature. Higher temperatures allow their muscles to contract more quickly and with greater force, thus cranking up the volume.

In essence, cicadas are nature’s thermometers. Their noise level is a reliable, if obnoxious, indicator of how hot it is outside. On sweltering summer days, cicadas hit their peak performance. Their calls become more frequent, louder, and sometimes even shift in pitch—just in case you weren’t already aware that it’s scorching outside. Researchers have found that you can estimate the temperature by counting the number of cicada calls in 25 seconds, dividing by three, and adding four. Yes, the cacophony can be transformed into a makeshift weather forecast.

In Japan, the most commonly heard cicadas include the “minmin-zemi” (ミンミンゼミ), “tsuku-tsuku-boushi” (ツクツクボウシ), and “abura-zemi” (アブラゼミ). Each species has its own unique call, adding layers to the summertime symphony.

So, the next time you find yourself gritting your teeth at the relentless cicada chorus in Japan, remember: their cacophony is a testament to the sweltering summer heat and a marvel of evolutionary adaptation. And maybe, just maybe, it’s their way of commiserating with us about the weather. Because if there’s one thing we can all agree on, it’s that summer heat makes everyone a little bit cranky—even the cicadas.