The Effect of Temperature on Running Pace

Despite 3 more months of training, I have not replicated my PR 5k time of 26:34 at the CB&I triathlon. I think the weather is largely to blame. CB&I was perfect running weather... probably 55 or so by the time I started running. Despite a best effort over the weekend, I only managed 28:58. This was a drop in pace of 0:50/mile. The heat was tough. The weather at run time was 85 F, but it felt like 95 F (that is what the weather report said it felt like, not just me).

How much doesn't the weather impact run time then? My heart rate for the run averaged at my Lactate Threshold of 184, so I don't feel like I was slacking. An online calculator shows a change of 0:19/mile from 60 F to 85 F and only goes up at total 0:27/mile at 95F.

What about real life data? I compared participants in the 30-44 male age groups from CB&I to Bridgeland. Including myself, there were 38 people that did both races. The median differential was 36 seconds per mile, with the 20th percentile at 18.4 seconds and the 80th percentile at 50.6 seconds. As with any statistics, there are outliers on both ends, but you never know the circumstances: e.g., if someone had stomach cramps at CB&I.

So real-world data indicates a higher impact of temperature than the calculator. Is the calculator wrong? Well, maybe the study that produced the data for the calculator only included only professional or elite athletes, who may have higher tolerance to the heat, or a variety of other reasons. My 50 seconds may be higher than the average, but it's not tremendously out of line, and doing this comparison has made me feel better about it.