Agreed that cold weather is easier to prepare for than hot. You can't dress for heat, as they say. You can, but nothing you can wear is actually going to make 105 degrees comfortable unless you happen to really love running when it's 105. I have and I found it way harder than any day I've run at minus 10 degrees F.
I will confess that as I get older, I am raising the lowest temp at which I will run outside. Used to be minus 20. Nowadays, I don't wanna run if it's below 0 F. I will if I'm meeting people, but I will wuss out if it's just a regular training run or nothing crucial like a 20-miler.