While extreme storms like tornadoes and hurricanes get most of the media attention, a far simpler weather condition – heat -- is much deadlier. Heat kills an average of 658 people every year -- more than tornadoes, hurricanes, floods, and lightning combined. In the disastrous heat wave of 1980, more than 1,250 people died. In the heat wave of 1995 more than 700 deaths in the Chicago area were attributed to heat. In August 2003, a record heat wave in Europe claimed an estimated 50,000 lives.

With summer just ahead, federal agencies are issuing warnings about the dangers of extreme heat.

“North American summers are hot; most summers see heat waves in one or more parts of the United States,” according to the National Weather Service (NWS). “East of the Rockies, they tend to combine both high temperatures and high humidity, although some of the worst heat waves have been catastrophically dry. “

People suffer heat-related illness when their bodies are unable to compensate and cool themselves properly. Extreme heat affects everyone, but the elderly, children, the poor or homeless, persons who work or exercise outdoors, and those with chronic medical conditions are most at risk.

Extreme heat can cause:

• very high body temperatures
• brain and organ damage
• death

Living alone can be dangerous

A study released last week in Center for Disease Control and Prevention's (CDDC) Morbidity and Mortality Weekly Report found that 7,233 heat-related deaths occurred in the United States from 1999 to 2009. An analysis of 2012 data indicates that deaths are on the rise. In a 2-week period in 2012, excessive heat exposure resulted in 32 deaths in four states, four times the typical average for those states for the same 2-week period from 1999-2009. More than two thirds of the deaths (69 percent) occurred at home, and 91 percent of those homes lacked air conditioning. Most of those who died were unmarried or living alone, and 72 percent were male.

The deadliest three states

According to CDC’s Environmental Tracking Network from 1999 to 2009 three states, Arizona, California, and Texas accounted for approximately 40 percent of all heat-related deaths in the United States. Across the nation, heat-related deaths occur more frequently among males and among adults aged 65 and older.

When you should worry

Each National Weather Service Forecast Office issues the following heat-related products as conditions warrant:

Excessive Heat Outlooks:  are issued when the potential exists for an excessive heat event in the next 3-7 days. An Outlook provides information to those who need considerable lead time to prepare for the event, such as public utility staff, emergency managers and public health officials.

Excessive Heat Watches: are issued when conditions are favorable for an excessive heat event in the next 24 to 72 hours. A Watch is used when the risk of a heat wave has increased but its occurrence and timing is still uncertain. A Watch provides enough lead time so that those who need to prepare can do so, such as cities officials who have excessive heat event mitigation plans.

Excessive Heat Warning/Advisories: are issued when an excessive heat event is expected in the next 36 hours. These products are issued when an excessive heat event is occurring, is imminent, or has a very high probability of occurring. The warning is used for conditions posing a threat to life. An advisory is for less serious conditions that cause significant discomfort or inconvenience and, if caution is not taken, could lead to a threat to life.

The role of government

CDC recommends that local governments engage in advanced planning and preparation to minimize deaths from extreme heat events and to heighten public awareness about the dangers of excessive heat exposure. Advance planning should include increasing access to air conditioning, cooling stations or other public locations that can be used by residents for temporary relief from heat, particularly when temperatures are elevated for several consecutive days.

“Heat-related illnesses and deaths are preventable. Taking steps to stay cool, hydrated and informed in extreme temperatures can prevent serious health effects like heat exhaustion and heat stroke,” said Ethel Taylor, DVM, MPH, the study’s lead author.

For more information on extreme heat from the CDC:

Extreme Heat and Your Health Website: This new page collects CDC resources on extreme heat in one place and provides information on how to prevent heat-related illnesses and deaths for a variety of audiences.

Climate Change and Extreme Heat Events Guidebook: This recently released guidebook for state and local health departments describes how to prepare for and respond to extreme heat events and explains how the frequency, duration, and severity of these events are increasing as a result of climate change.