Of all the factors listed in the OP, ambient temperature jumps out at me as being somewhat different. I find that in heat, you really need to be really conscious of regulating your pace or face putting yourself into actual physical danger. I have to ride fast enough to keep adequate airflow, but not to make so much of an effort that my body can't regulate its temperature. I did a couple of very hilly 80 mile rides in 90+ degree heat last summer (1 day apart), and there were places at tops of long climbs where the only prudent thing I could do was to take a few minutes off of the bike in the shade. When you're going too slow to quickly evaporate sweat, any effort heats you up very fast so hills can be deadly. So basically, it's a factor that punishes you if you go too fast or too slow.