|Heat: A Major Killer||Heat Index Forecasts||UV Safety||Michigan Heat Awareness Brochure (PDF)||Heatwave Brochure (PDF)|
What exactly is a heat wave?
A heat wave is a prolonged period of excessive heat and humidity. An Excessive Heat Warning is issued if the heat index equals or exceeds 105° for at least three consecutive hours. Excessive Heat Advisories are posted when the heat index is expected to exceed 100° for two consecutive days or if low temperatures are higher than 80°.
What is the Heat Index?
The heat index is a measurement of how hot it really feels when the relative humidity is incorporated with the actual temperature. Heat indices were designed for use in the shade with light wind conditions. If in direct sunlight, the heat index can increase as much as 15°. With very hot and dry air, strong winds can also be extremely dangerous.
|Category||Classification||Heat Index/Apparent Temperature (0F)||General Affect on People in High Risk Groups|
|I||Extremely Hot||130° F or Higher||Heat/Sunstroke highly likely with continued exposure|
|II||Very Hot||105° F - 130° F||Sunstroke, heat cramps, or heat exhaustion likely, and heatstroke possible with prolonged exposure and/or physical activity|
|III||Hot||90° F - 105° F||Sunstroke, heat cramps, or heat exhaustion possible with prolonged exposure and/or physical activity|
|IV||Very Warm||80° F - 90° F||Fatigue possible with prolonged exposure and/or physical activity|
As temperatures and humidity climb, the body has to work harder to maintain a constant temperature of 98.6°. Ninety percent of the body cooling process is done by evaporation of water through the skin, or sweating. Higher relative humidity slows the evaporation rate and cooling process. Heart rates increase trying to pump more blood through the body, that in turn, evaporates more liquids from the body. When the heat gain exceeds the level of heat the body can remove, or when the body cannot compensate for fluids and salt lost through perspiration, the temperature of the body begins to rise and a heat related illness may develop.
Ranging in severity, heat disorders share one common feature: the individual has overexposed or overexercised for his/her age and physical condition.
Four types of heat disorders that occur and their symptoms include:
All heat disorders require attention, but heat stroke is a severe medical emergency and requires immediate medical attention. Any delays can result in death.
Following some simple safety tips can help prevent heat related problems: