I kind of ended up backing myself into a corner this morning, as I pushed back my 20 miler from yesterday to today as the weather reports indicated that it would be cooler. Unfortunately, it ended up being about the same around here, so I was left with little choice but to head out into the 40C+ (104F) temperatures and fight through it. Due to a couple of heavy runs near the end of last week I couldn't push it to Saturday, and with another heavy week coming up I couldn't really push it to Tuesday either.
At first it wasn't too bad, with the humidex floating around 38C (26.3C ambient + 93% humidity) and overcast skies it wasn't exactly comfortable, but it was bearable. While the heat wasn't a big problem, the soupy air was still pretty difficult to breathe which made things significantly more difficult than I would have liked. Either way, I focused on controlling my pace to make sure I didn't push too hard and create a problem, although it was difficult to put down that mental focus in an environment like this. I wasn't able to slow myself down as much as I would have liked, but I was still quite comfortable and my fluid reserves were doing pretty well.
Unfortunately, about 45 minutes into the run the clouds parted and the sun started shining through. The ambient temperature had creeped up into the 30s at this point, and while the humidity was a little lower the humidex was well into the 40s. As such, the sun beating down on me was making things considerably more difficult and my heart rate was running a bit higher than I would have liked. I started taking in more fluids to offset this, and that worked well for a while but it also meant that I was draining my supplies faster.
Just after the 14K mark (about 1:15 into the run), I stopped into a 7-11 and picked up another bottle of Gatorade to refill my bottles. Once topped off, I continued on but at this point the heat was beginning to hit me harder than it had before. I tried to refocus on backing off the throttle a bit, which helped, but the humidity meant that my sweat wasn't evaporating so my core temperature was climbing and making it more and more of a fight.
Just before the 18K mark (~1:33), I pulled into a community centre to cool off a bit and get some water. When I restarted, it was evident that it was going to be extremely difficult to get in the full distance as my HR was continuing to run significantly higher than normal, and the rest stops weren't really doing a lot to help with that. As such, I refocused my aim to make it to the Running Room shop and then play it by ear - if things continued along the route they were going, that would give me the option to abort and call for a pickup.
Over the next few kilometers I ended up burning through the Gatorade that I had left, and things were getting progressively more difficult. I took a few short breaks to allow myself to cool down, but looking at my heart rate it was evident that it would be unwise to try to get the full distance in - while I could likely have done it, it would have significantly increased recovery time and potentially hurt the quality of the other runs this week. As such, I sped up a bit over the last few kilometers and headed over to the shop. Once I hit the 23K mark, I fell back to a walk, then stopped out front and did my stretches. I popped in, made my call and then bought some more Gatorade and cooled off while I waited.
As much as I hate quiting early, especially on these critical 20 milers, I have to look at it from an overall perspective. I could have restocked my bottles at the RR and continued on, but doing so would have left me significantly depleted and likely would have hurt more than it would have helped. In retrospect, heading out on Sunday morning would have likely been the better bet - the temperatures were about the same, but the skies stayed overcast so there was no sun to fight with. Either way, I made the decission that I did based on the best information that I could find - unfortunately, weather forecasting is an inexact science so it's difficult to work around problems like this :(