How hot is too hot? When it comes to outdoor training, at what point do you draw the line?
New York has been in the grips of a heat wave all summer - when it's not raining (or dark out) - the temperature is consistently in the upper 80s to upper 90s, with a few triple digit days thrown in. That's hot. Granted, it's not Badwater Ultramarathon HOT, but it's certainly danger zone hot for us mere mortals who aren't necessarily accustomed to running in this weather.
Personally, unless I'm knee deep in marathon or ultra training, I avoid running outdoors in this weather. If I can, I'll get out there for an early morning run (starting before 7 am) or an evening run (once the sun's gone down). I'll also take pains to plan routes that incorporate as much shade as possible (trails by me are great for this) while avoiding spots that I know are notorious for pounding you with sunshine (portions of my Lake run are killer).
Another strategy that I find useful when it's overwhelmingly hot during long training runs - loops. They're boring, but they're virtually fool-proof. Hot weather means more liquids. I make sure that in addition to whatever I'm carrying, I have stashed liquids that I pass by at least once per hour. Just make sure you don't pass your car too often - the temptation can be too great to call it a day and head home :)
The toughest thing to remember in this heat is that you've got to dial down the intensity. Put away the watch, stop looking at your pace, and just listen to your body. Unless you're well acclimated to heat and humidity, you're going to have to slow it down. Perhaps even trim the distance.
Remember that we run because we like to. Keep it enjoyable, keep it real and keep it safe.