Japan’s earthquake shows extreme heat can turn one disaster into two

A recent earthquake in Kyushu, Japan, killed at least 38 people and left thousands homeless in late July. The disaster was exacerbated by extreme summer heat. Daytime temperatures soared into the high 30s and reached 40°C for the first time ever, accompanied by high humidity. The heat affected almost every aspect of the emergency response.

Over 7,000 people in 130 evacuation shelters and temporary accommodations faced increased risks of dehydration, heat exhaustion, and heatstroke, especially vulnerable populations like older adults, infants, and those with chronic illnesses. Heat also made it harder for people to sleep, which in turn worsened stress, impaired decision-making, and slowed recovery from traumatic events.

Emergency responders, who were already engaged in physically demanding rescue work, debris removal, and infrastructure repairs, were similarly impacted by the extreme heat, reducing their physical performance, increasing fatigue, and necessitating more frequent rest breaks. The heatwave also strained water supplies and electricity, as cooling demands rose alongside power outages.

This created a second emergency that received far less attention than the earthquake itself but posed significant threats to public health and recovery. This compound event illustrates how natural hazards can interact, amplifying their combined impacts. The 2026 conditions are starkly different from those of the 2016 Kumamoto earthquake, when temperatures were milder.

As climate change intensifies, disasters like these will increasingly involve both primary and secondary hazards, underscoring the need for comprehensive disaster resilience planning.