Japan's Farmers Turn to Night Work as Heatwaves Turn Deadly
Record heatstroke deaths push Japan's ageing farmers to work at night, reshaping agriculture as heat costs billions in lost labour.
In Nikko, north of Tokyo, Motoaki Iijima's greenhouse glows after sunset as he harvests gerberas, a routine born of necessity. Three years ago, a worker collapsed from heatstroke in his sunflower field. Now, with outdoor temperatures regularly exceeding 35°C and greenhouse interiors topping 40°C, Iijima and his team work through the night, stopping only when the morning sun becomes unbearable.
"The hours around dusk are really precious," he says. "We've gradually become nocturnal. It's about protecting our bodies, and ultimately, our lives."
The shift is not isolated. Across Japan, farmers are abandoning midday work for cooler hours. The numbers explain why: a record 59 agricultural workers died of heatstroke in 2024, more than double the toll in 2021. About 70% of Japan's farmers are 65 or older, making them especially vulnerable to heat stress, and high humidity worsens the danger.
A survey by the Japan Weather Association found that nearly 60% of farmers in their 20s to 50s had either suffered heatstroke or knew someone who had. Almost the same share had moved their working hours to earlier or later in the day.
The economic cost is steep. Lancet Countdown estimates that heat exposure cost Japan's agricultural sector 926 million potential labour hours in 2024. Across all sectors, lost hours nearly doubled from the 1990s average, translating to roughly $46 billion in lost income, or about 1% of GDP.
On Iijima's farm, veteran worker Miyoko Asada, 68, arrives shortly after sunrise to cut asters before temperatures climb. "We've got to race against the clock," she says.
Poultry farmer Tetsuya Usuba faces a different crisis. Six years ago, he lost over 500 hens to heatstroke in a three-day heatwave. Now, lights in his barns flick on at 2:30 a.m. to wake his 4,400 hens so they eat before the heat suppresses their appetite. He has added fans, sprays water on roofs, and puts citric acid in drinking water. Still, last month's spike above 35°C killed 130 birds. "Summer has become a new threat," he says, "something as scary as an outbreak of avian influenza."
The government has responded with new workplace regulations in 2025 requiring heatstroke reporting and emergency plans, and is promoting smart farming tools like drones and robots. But for now, adaptation on farms like Iijima's remains manual and urgent. As workers load flowers before 8 a.m., one calls out that leaves are already wilting. Iijima glances at the overcast sky. The heat will return.