Summer 2010 was a hot one for New York City. Spring came early, and once the warm weather set in, it didn’t lift for most of the summer. A heat wave in July brought temperatures to the triple digits for several days, in and around town. People were desperate for relief. Hydrants were hacked; hoses, uncoiled. Side streets became mini water parks. Pool admissions were up.

July 6 was the real scorcher. It reached 103 degrees that day—breaking an eight-year record. According to the New York Daily News, since 1869, when officials began to keep temperature records in New York City, only three days have been hotter.

That was a busy day for the New York Fire Department’s Emergency Medical Service. It received 4,225 calls, about 30 percent more than usual, the New York Times reported. It was the fifth busiest day for the service in eight years.

When you call 911 in New York City, you first talk to a call-receiving operator called a CRO. (There are a lot of annoying acronyms in emergency medicine.) The CRO is trained to ask a series of questions to determine whether the emergency requires medical attention. If it does, an emergency medical services (EMS) dispatcher—who is trained as an emergency medical technician (EMT)—gets conferenced into the call. The EMS dispatcher determines what level of response is required: the most serious calls—“segment 1s”—are choking, cardiac or respiratory arrest, and drowning. Segment 1s always get two paramedics, two EMTs, and a team of certified first responders (CFRs), plus the cops often show up.