2 and a half hours of What?

My plan to break long runs into smaller segments is sort of working, but why am i still totally exhausted and i feel as if i'm hardly moving?  Yesterday the heat index was about 90, and i first went out for a brisk 25 minutes before I had to deal with the kids.  Then at 10 i went out for what became two and a half hours of slogging, just to get the volume in.  I was all tricked out with fluids and nutrition, but my fatigue was so unsettling as I left my house that I decided to walk until I felt like running.  I walked for a full 50 minutes before I even bothered to run or jog.  Once I got started everything was OK, and I then walked a few more times, but for shorter periods.  Whatever this summer is, it is Not a summer of training fast.  So did it all add up to 18 miles? there's no chance of that.  My total time for the day was only 3 hours, and with an hour of walking, well, let's just say that i did the best I could on that given day.  Today I'm still feeling the aftereffects of the heat and fatigue.  I made it out for my morning loop ride, but i'm resting for the remainder of today.  Time to bank some recovery and avoid the heat of this place.