A 65-year-old Prince George's County man was outside in Monday's heat, cutting the grass with a push mower. He quit, went inside, collapsed and later died.
Not far away on the same day, a 79-year-old Pasadena man was found dead, alone in his home. The windows were closed, and indoor temperatures had climbed above 90. County fire officials said the house had electricity but that the air conditioners were not running.
The medical examiner's office has ruled that both deaths were the result of heart disease complicated by hyperthermia. They were the first heat-related deaths reported in Maryland this year, a consequence of four days of 90-plus temperatures and high humidity.
Anne Arundel County Executive John R. Leopold called the Pasadena death "an avoidable tragedy." In a statement, he urged residents to "check on your elderly neighbors to ensure they are doing all they need to do to keep cool as temperatures soar."
Maryland Secretary of Health John M. Colmers said: "Everyone should be careful in hot weather, especially elderly people, young children and the overweight.
"While chronic health conditions such as heart disease, diabetes and respiratory illnesses increase an individual's risk, there are things people can do to protect themselves."
Authorities did not release the victims' names.
Last year, 21 heat-related deaths were reported in Maryland, less than half the number reported in the previous two years - 43 in 2006 and 47 in 2006. Over the winter, 14 Marylanders died in circumstances related to cold weather.
The elderly and those with chronic health conditions are especially vulnerable in both weather extremes.
"The elderly, whose heat-compensatory mechanisms work a little more slowly, may not be as aware of getting into trouble from the heat," said Dr. Michael A. Kent, an emergency room physician at Anne Arundel Medical Center in Annapolis.
That is the exception. Generally, he said, when the body's cooling mechanisms fail, "that's where most people start feeling sick. They feel nauseated, with headaches."
The high temperature Monday at BWI Marshall Airport was 94, more than 10 degrees above the long-term average for the date. It was the third straight day of 90-plus weather and high humidity across the region and the first summerlike heat of the year.
"It catches people off guard ... and unprepared with cooling," Kent said.
Medical experts say heat kills by overwhelming the body's two primary cooling mechanisms: the evaporation of sweat from the skin and the release of body heat from blood vessels near the skin. The cooling process is slowed by high humidity.
Age and chronic cardiovascular conditions can hamper the body's efforts to cool itself.
Heat exhaustion occurs when sweating leads to the loss of too much fluid and vital electrolytes. Victims experience nausea, vomiting, weakness, muscle cramps, headache or fainting. Those with cardiovascular disease can suffer heart attacks as their hearts struggle to deliver blood to the skin to cool.
Treatments include fluids and rest in a cool, shaded area.
If the body temperature exceeds 105, a person will experience heat stroke, characterized by dry, red skin, convulsions, disorientation, delirium, organ failure and death.
Dementia, obesity, high blood pressure, diabetes, dehydration and alcohol use can also increase the risk of heat-related illness.
To stay safe in the heat, experts advise drinking plenty of water or fruit juice, and avoiding alcohol, antihistamines and diuretics. Wear loose, light-colored clothing, a hat, sunglasses and sunscreen and avoid direct sunshine. If possible, stay in air-conditioned areas and avoid strenuous outdoor activity.