People walk with parasols after the Kinki region's rainy season officially ended, Chuo Ward, Osaka, July 8.
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Japan is heading into what Yasufumi Miyake describes as an unusually risky stretch for heatstroke—not because this summer is hotter than others, but because the heat has arrived so suddenly.
"This year really is a different type of summer than we've had in recent years," said Miyake, who has served on a medical society's heatstroke countermeasures committee since 2006, in an interview with Japan Forward.
A Body Unprepared for Summer
In a typical year, Japan warms up through June, the rainy season ends early, and a long, gradually intensifying summer follows. This year broke that pattern: June was unusually cool across the Kanto region, and heatstroke-related hospital transports—tracked weekly by the Fire and Disaster Management Agency—stayed low as a result.
But Miyake warned that the calm is about to end. "Once the rainy season ends in both western and eastern Japan, full summer heat is going to hit bodies that haven't gotten used to the heat at all."
The body builds tolerance to heat gradually, Miyake explained—the ability to sweat efficiently and shed heat through the skin develops over days and weeks of exposure. Without that buildup, "the stress heat puts on the body is considerable," particularly for anyone active outdoors: laborers, students doing PE or club activities, and even people simply running errands or picking up children.
He pointed to hospital data showing the last ten days of July are historically Japan's peak period for heatstroke-related hospital visits. "If that peak is coming and there are only about ten days left until the end of July, it's going to be a sharp spike. I think the risk of a sudden surge in heatstroke cases is high this year."
Rather than trying to build up heat tolerance now through exercise—a method Miyake said typically involves 30 minutes of walking or 15 minutes of jogging—he argued that it's the wrong move under current conditions.
"Trying to do that kind of preparation in this heat is actually dangerous. At this point, it's not about preparing for the heat anymore—it's about preventing heatstroke itself."
He recommended ramping up work or activity gradually instead: starting at 60-70% of normal intensity, adding more frequent breaks, and shifting the most demanding tasks away from the hottest part of the day.
Who's Most at Risk, and Why
Miyake described different mechanisms behind the risk facing older adults, children, and outdoor workers.
For the elderly, he said the priority is simple avoidance—staying indoors with air conditioning running, and having family or neighbors check in, since many older Japanese live alone. "We're only about a month from the peak, so if people look out for each other during that stretch, we can get through it."
For children, he suggested cutting outdoor activity time in half and using the rest for indoor breaks.
For workers, he pointed to the same gradual ramp-up approach, adding that Japan's heatstroke-prevention workplace campaign, backed by penalties since last year, reflects a push by regulators.
However, he noted that the aging of Japan's blue-collar workforce makes continued vigilance necessary.
Do the New Workplace Rules Actually Work?
A year after penalty-backed workplace heatstroke rules took effect, Miyake was cautious about declaring success. Fatality data looks low, "but a low number of deaths doesn't mean the number of people affected is low—that's just the number that gets formally reported as a labor accident."
He suspects many milder cases, especially among children cared for at home overnight, never appear in official statistics. In his analysis, the health ministry's new March 2026 workplace guidelines were "a preemptive move rather than a reaction to a wave of cases."
A Misconception Worth Correcting
The most dangerous mindset, Miyake said, is overconfidence among older people who assume past resilience predicts future safety.
He recommends practical fixes, such as having family members prompt elderly relatives to turn on the air conditioning when a room thermometer reaches 28-30°C (82–86°F).
For youth sports, he says coaches or parents—rather than players eager to compete—should decide when to rest, cool down in shaded or air-conditioned spaces, and drink chilled rather than lukewarm water.
What Other Countries Can Learn
Asked what lessons Japan's approach offers overseas readers, Miyake pointed to the administrative infrastructure Japan has built specifically for heatstroke: cool shelters designated by the environment ministry, and a heatstroke alert system with an unused "special warning" tier already in place.
Doctors themselves, he added, aren't really the deciding factor in whether heatstroke turns fatal: what matters most happens before a doctor is ever involved—cooling the body, hydrating, resting. "Those things have to happen at the scene, not at the hospital."
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Author: Daniel Manning
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