I find my average HRs for intervals and races and such is VERY dependent on the temperature. I guess that makes it less reliable for me, but I sort of can tell by now how many beats to add when it is hot and humid. Also, when my HR is abnormally low for a workout, it generally means my legs are wicked tired. But, everybody is different, and everybody's hearts act differently.
Way to be speedy, speedster =)
Interesting, may try adding temp data to that list, see how that goes.... Certainly the PR day wasn't as hot as recent one...
Temp affects my HR a lot too. Excited to see how speedy you're looking before WOC!
Temp also affects me, but not much for hard efforts. The difference is large for easy efforts.