The Department of Health and Social Services says the 55-year-old man, of New Castle County, was found unresponsive outside Wednesday.
The victim's death is being ruled an accident.
The Medical Examiner says the victim had an underlying health condition, though the heat exposure contributed to his death.
DHSS reminds people to have an emergency plan during a heat wave, just as one would for a hurricane or snowstorm.
The department says symptoms of heat exhaustion include dehydration, fatigue, clammy skin, headache, nausea or vomiting, hyperventilation and fainting.
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