Marathon runners(Miguel A. Amutio / Unsplash)For the best performance when running, it’s smart to take into account temperature and humidity. Find out why with this installment of Science Behind the Forecast.This transcript was edited for clarity and length.Bill Burton: It's time for us to take a look at the Science Behind the Forecast as I'm joined by WAVE 3 meteorologist Tawana Andrew. Good morning, Tawana.Tawana Andrew: Good morning. Today's topic is for the runners, which we are walkers, not runners.BB: I prefer a slower pace, but for those who do like to run, they always like to know the best temperatures to run in. So that's what we're talking about today.TA: The heat is not really the thing for anybody, I think. But specifically for runners, the heat and humidity can negatively impact your running performance.High temperatures change how our bodies use energy and regulate heat. As the body starts to prioritize your internal temperature over speed, a runner's performance will degrade.In hot temperatures, our bodies need more oxygen, since some of that blood flow is being redirected from running whatever pace that you need to run, to actually cooling off. That's what increases your heart rate, increases energy usage, and lactic acid production. That's why it feels like you get more cramps in those hotter temperatures. Your body is trying to get that oxygen moved around. I, of course, nerded out on the numbers.BB: I love that about you.TA: Experts say that when running more than half a mile with temperatures over 77 degrees Fahrenheit, which is most of the summer around here, race times can actually decrease up to 3%. In temperatures between 50 and 64 degrees Fahrenheit, endurance runners can see their performance actually improve.For sprinters, on the other hand, the data shows that their performance can improve 1 to 2% in hotter temperatures. I guess for the shorter distances, the heat doesn't impact you as much, but if you're doing more endurance running, you're doing marathons, maybe an Ironman, you want those cooler temperatures.Research has found that the optimal range for marathon runners is between 44 degrees Fahrenheit and 59 degrees Fahrenheit. Unless you're outside of that range, your finish times are going to be slower on average. For those of you who want to break that personal record, the spring and the winter runs would probably be the ones to do.BB: Sounds like the wise choice.TA: Plus, you don't have to deal with all that heat!BB: That part is not fun at all.TA: Experts found that runners with a 5:45 pace or faster saw a one second per mile reduction in speed for every about two degrees Fahrenheit in temperature. For those of you with a 10:00 pace per mile, that slowed to around four to five seconds per mile for each two degrees Fahrenheit above 59 degrees. The cooler you are for marathon runners, the better you will be, for sure.Humidity also plays a role with this, because humidity can limit sweat evaporation, inhibiting your body's ability to perfectly cool off. You need that evaporation for your temperature to drop. Humidity starts to affect athletic performance once it's over 35%.That is something to keep in mind, because around here we typically see that type of lower humidity in the spring, in the fall, and in the winter months, not as much in the summer. Once the humidity jumps to around 75%, a runner's pace can drop by about 6%. Keeping an eye on those temperatures, keeping an eye on humidity, all very, very helpful in making sure that you're running the pace that you want. ...read more read less