You can almost die on a 6-mile run.

Sunday morning I got up a little late and stumbled out the door for 6 miles of soft-surface running. Since we got a lot of rain over the past week, the outside loop of Audubon park was out of the question: rain turns it into a bog. I opted instead for the streetcar tracks, which dry out faster, and promised to be mostly runnable.
I almost died.
I got out the door at close to 8 am, and it was 88 degrees. Not bad, really; I've run in much worse. But the humidity was stifling. There was a damp dome of moisture above me, through which the sun was beating down. For about a mile, I was just trucking along. Then somewhere in mile two, I decided that I was going to die in about 5 minutes. My clothes were saturated with sweat and being annoyingly clingy. My shoes were squelching with mud and sweat. My head throbbed in the heat. I kept squinting angrily to keep the sweat from pouring into my eyes.
To make it worse, I was running into a steady headwind that felt like a public bathroom hand-dryer. Somehow I survived until the turnaround point, and things got much better: the wind was behind me, and it brought in clouds that occasionally provided respite from the sun. A storm was rolling in, which explained the incredibly heavy air, but the shade was worth it.
Somehow I didn't die, even though I was pretty sure death was imminent, but I felt terrible the rest of the day. I was light-headed and had no appetite, and just moped for several hours. Finally I remembered that whole electrolyte thing and had a pinch of salt. Ah! Revival! That made a big difference. But man, it was still a rough day.

I have a feeling that my new, slower self (never got under 8:30 pace Sunday) is going to struggle this summer.