Heat Wave Disasters

Definition

A heat wave is a period of abnormally hot and humid weather. Like cold waves, heat waves are relative to the local norm. Heat waves, therefore, represent a significant departure from normal seasonal temperatures. The comfort criteria for heat waves in any region depend upon acclimation to the usual conditions.?

Speed of onset and duration

A heat wave as such a period should last at least one day, but conventionally it lasts from several days to several weeks. Heat waves are typically seasonal, with most incidents occurring during summer.?

Consequences

Heat waves are known to cause extensive impacts on human morbidity and mortality while leaving infrastructure largely undamaged. Besides causing overutilization ofing health care resources, heat waves can also result in power outages that further exacerbate heat illness by disrupting cooling and ventilation. Power shortages can also affect transportation, communication, and health care systems. Heat waves can expose outdoor workers to extreme heat or when working in hot environments, and especially putting those in tropical low-middle- income countries are at increased risk. Heat waves have also been associated with secondary disasters, including air pollution and wildfires.?

Scale

During the past 60 years, 209 heat wave disasters were reported worldwide that caused an average of 804 deaths per incident. Heat waves can affect an entire city or even a region. In 2003 one incident resulted in tens of thousands of excess deaths throughout Italy, France, Spain, and Germany. In 2010, one heat wave affected millions of persons throughout western Russia, including Moscow.?

Several scales have been offered to describe the severity of heat waves. The heat index (i.e., apparent temperature) is widely used. It approximates how hot it "feels" for ambient air temperature and relative humidity. Simply put, relative humidity measures the water vapor in the air. Generally, higher values at the same temperature feel warmer and more stressful because of less evaporative cooling when people perspire.?

An excess heat factor, (commonly referred to as an EHF) has been proposed as an index for relating heat wave intensity and severity. The factor is, based upon a three-day- averaged daily mean temperature.?

From: Keim M. Emergency Health: Practical Application of Public Health Principles. APHA Press. 2023 See: https://secure.apha.org/imis/ItemDetail?iProductCode=978-087553-3346&CATEGORY=BK