Heat waves, heat index, excessive heat warnings, and dangerous temperature events
This extreme heat monitor tracks dangerous heat events worldwide, combining air temperature with humidity-adjusted heat index values to show how dangerous conditions actually feel. Users searching for heat wave today, heat index near me, or excessive heat warning can see active alerts and peak temperatures globally.
Heat index — also called apparent temperature — combines air temperature and relative humidity to express how hot conditions feel to the human body. At 35°C with 70% humidity the heat index reaches 50°C, well into the danger zone where heat stroke is possible with continued exposure. The wet bulb globe temperature (WBGT) is the more rigorous metric used for athletic and occupational safety thresholds, factoring wind and radiation alongside temperature and humidity.
A heat wave is typically defined as a period of at least three consecutive days with temperatures above the local 90th percentile for the season. National definitions vary — the UK Met Office uses regional thresholds from 25–28°C, while heat-adapted regions require much higher absolute temperatures. The wet-bulb temperature threshold of 35°C represents the physiological limit beyond which even healthy humans cannot dissipate heat through sweating.
Extreme heat is the deadliest weather hazard in many developed countries, killing more people annually than tornadoes, hurricanes, and floods combined. Heat exhaustion progresses to heat stroke when core body temperature exceeds 40°C, requiring immediate cooling and medical attention. The elderly, infants, athletes, outdoor workers, and people with cardiovascular conditions face the highest risk. Urban heat islands intensify exposure in cities, where pavement and buildings trap heat.
Heat waves are becoming more frequent, longer, and more intense as the global climate warms. Record-breaking heat events that historically occurred once per decade now happen multiple times per decade in many regions. Marine heat waves are also intensifying, disrupting fisheries and coral reef ecosystems. Adaptation strategies include cooling centers, building codes for heat resilience, and early warning systems.
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