It was hot and very muggy -- about 28 degrees, I suspect, when I started the run, although I waited late enough into the day that the sun was behind the clouds. Humidex would have had it well into the mid-30's, I'm sure.
My plan was to do 3 miles at long run pace, then 3.5 miles at a tempo run pace of between 4:37 and 4:40 per kilometer, and the .5 miles of cool down. The first 3 miles were fine, naturally, and so were the first couple of miles at the tempo pace. But then I started to feel the heat and it got tougher and tougher for me to keep the pace. I finally gave in at about 2.7 miles into the tempo run and had a walk break. After a couple of minutes, I was able to get right back on pace and finish the 3.5 miles at tempo pace -- but it was tough. And the last kilometre of cool down was sloooooowwww.
My warm-up laps were at the following pace: 5:21, 5:06, 5:16, 5:17 and 5:18 per kilometre (targeting 5:20). My tempo laps were at the following pace: 4:40, 4:41, 4:37, 4:41 and 4:39 per kilometre (targeting 4:37 to 4:40), and my cool-down lap was in excess of 6 minutes/kilometer.
A tough run, but I made it through relatively unscathed!