In July 1995, the Midwest experienced a devastating heat wave that killed 465 in Chicago and 85 in Milwaukee. Although this event was rare, it is believed that a higher frequency of heat waves can be expected in the years to come due to global warming.
Heat waves can effect any human being whether athletic or not, especially, the very young and elderly citizens. The greatest concern are those citizens who live in urban areas due to the Urban Heat Island effect. The Urban Heat Island effect is a concept where temperatures will be higher due to the lack of green space and the absorption and emission of heat energy by human-made objects.
Although urban centers can be of great concern, rural environments can also be the scene of devastating heat. During the growing season, plants release moisture into the air, which can increase dew point temperatures and relative humidity, resulting in higher apparent temperatures. High moisture values in the air is the main culprit of heat waves.
Heat waves are the result of upper air ridging where the jet stream shifts to the north. Within this area, warm surface temperatures occur. If the jet stream is positioned to the extreme north of a location, temperatures can significantly increase. Warm surface temperatures combined with high relative humidity values or high dew point temperatures can increase the apparent temperature, the temperature felt by the human body.
How to protect yourself and others
When an Excessive Heat Advisory/Watch/Warning has been issued by National Weather Service for a region, it is important to follow these quidelines to protect yourself and others from heat related injuries and deaths.
- Reduce the time spent outdoors.
- Increase the intake of liquids. Water and non-caffenated drinks are the best. Alcoholic and caffenated beverages increase dehydration.
- Remain in air conditioned buildings/structures. If you do not have air conditioning, visit a public place such as a Mall. The use of fans may provide those without air conditioning some relief but can still be harmful as it does not increase comfort but only circulates the same hot moist air.
- If you must be outdoors (i.e. job related activites), wear lightweight clothes that are bright in color such as white and/or yellow. Bright colors reflect solar radiation while dark colors absorb energy and increase the body's apparent temperature.
- While public pools are sometimes a great place for relief, high UV Index values can increase the potential of heat related injuries caused by sunburns.
- Periodically monitor elderly neighbors as they are extremely susceptible to harsh conditions.
- While heat waves can affect the human species, animals are also extremely susceptible to high temperatures. Provide plenty of water and shade for pets or bring them indoors.
- High temperatures and high relative humidity values increase the influence of surface air pollution, which can increase health risks.
The Heat Index
The heat index is a good indicator of how the human body will respond to an increase in the apparent temperature. The index is based on the combination of the air temperature and relative humidity. As the temperature and relative humidity increases, the health risk increases. Below is the Heat Index table that describes how the body will respond to elevated temperatures.
Category |
Apparent Temperature (F) |
Heat Syndrome |
I |
130F or higher |
Heat stroke imminent |
II |
105-129F |
Heat stroke, heat cramps or heat exhaustion likely. |
III |
90-104F |
Heat stroke, heat cramps, or heat exhaustion possible with prolonged exposure and physical activity. |
IV |
80-89F |
Fatigue possible with prolonged exposure and physical activity. |
Summary
As global warming continues, it is important to be aware of the influence of heat wave events on the human body. The best way to protect yourself from heat related injuries is to listen to your body. If you feel tired during hot muggy days, this is the body's message that it is stressed.