Does the impact of temperature on running performance increase with distance? This would mean something like for a 5k maybe a decrease of 3% in avg pace but for a half marathon a decrease of 8% avg pace. These numbers are just random values to try and make the question clear. Also Im asking in respect to the hot side of the ideal 50-60F running temps.
Yes, it does. Higher temperature acts as a catalyst when it's comes to your body's energy expenses. Your body does spend more calories, and loses energy faster compared to when it's cold. Lowering of the pace would result in maintaining the balance with high temperature environments. I don't know the exact figures, but on a very hot day performance degrades on a long run. Short sprints may not be affected by the temperature though.
Having said that, 50-60 F would be average or ideal temperature for the body while working out. What I said above applies to 90F and above.