Since Dew Point is a more useful measure of the water saturation of the air and thus its effect on our body while we run, I am recommending using it (rather than relative humidity), in conjunction with air temperatures, in determining warm weather pace adjustments to training.
The revised training pace adjustment formula is as follows:
Add together air temperature and dew point and see where the combined number places you on the following adjustment chart:
100 or less: no pace adjustment
101 to 110: 0% to 0.5% pace adjustment
111 to 120: 0.5% to 1.0% pace adjustment
121 to 130: 1.0% to 2.0% pace adjustment
131 to 140: 2.0% to 3.0% pace adjustment
141 to 150: 3.0% to 4.5% pace adjustment
151 to 160: 4.5% to 6.0% pace adjustment
161 to 170: 6.0% to 8.0% pace adjustment
171 to 180: 8.0% to 10.0% pace adjustment
Above 180: hard running not recommended
Note: a range is given as there are numerous individual factors, such as the size, fitness and physical make-up of the runner, and their level of acclimatization to the heat and air saturation levels, that will play into how much of a pace adjustment is needed.
The above are the pace adjustment percentages to use for continuous runs. For repeat workouts such as 400’s 800’s, or mile repeats, I recommend using half of the continuous run adjustment as the body has a chance to cool somewhat during the recovery between repeats.
For those who want help doing the math for these adjustments the following charts calculate the adjusted pace for various paces and % adjustments.
At the time of our planned continuous run the air temperature is 74 degrees and dew point if 71 degrees - a typical early morning in summer over much southern United States this summer. We would add these 2 numbers together to get 145 (74 + 71).
According to our chart, a total of 145 calls for a pace adjustment of 3% to 4.5%. We had planned to do our run at 7:00 pace under normal conditions, so we adjust the 7:00 pace by 3% to 4.5% and get an adjusted pace range of 7:13 to 7:19 per mile.
If, under those same weather conditions we had planned to run 8 x half mile repeats at 3:00 per repeat (6:00 per mile pace). We would cut the 3% to 4.5% pace adjustment in half and use a 1.5% to 2.25% pace adjustment. A 1.5% to 2.25% on 6:00 pace is a 6:06 to 6:08. So instead of targeting 3:00 per half mile, we would have an adjusted target of 3:03 to 3:04 per half mile.
Most of the pace adjustments obtained using this method align very closely to what I have shared previously when using relative humidity to adjust air temperature; but I believe the use of both dew point and air temperature to be a more accurate basis for the adjustment calculations, so I am offering this modification.