This Is How Much Slower You Run in the Heat
The same running workout on a hot day is more difficult than on a cool day, and it’s not just your imagination. We do slow down in the heat – at least until we adjust to it – and we can accurately calculate how much.
The Runners Connect temperature calculator is designed with race times in mind, but it also works well for determining what’s going on with your daily run. Today, for example, I skipped my early morning run and reformed later in the afternoon in the 80-degree heat. The calculator tells me that at my speed of about 10 minutes of miles, I should expect every mile to take about 15 seconds more today than it did last week at 65 degrees in the morning.
A heat on an 80-degree day increases your time by 20 percent over your pace on an ideal 45-degree day , while a day on a 70-degree day only adds 7 percent. This means that your exact deceleration will depend on your original time. Since calculating percentages with minutes and seconds is difficult, this calculator is a handy tool.
Humidity above 60 percent will slow you down even more, but it doesn’t show up on the temperature calculator. Relax on hot days and don’t be discouraged if your runs aren’t as fast as usual.
Temperature calculator | Runners connection