Here’s the thing about running in the heat: it’s a lot like running on a steep incline or at altitude. When you’re climbing hills or running at elevation, you don’t expect to maintain the same pace you would on flat ground.

The same is true in the summer heat. Don’t judge your fitness by the pace on your watch. Judge it by your effort.

The good news is that you’re still making gains. Just like hill training makes flat roads feel easier and altitude training makes sea level feel more manageable, training through the heat pays dividends when the temperatures finally cool off.

Just like you wouldn’t tackle a mountain on your first day of hill training, don’t jump straight into long runs in 100-degree weather. Build your heat tolerance gradually with shorter runs, stay on top of your hydration and electrolytes, and if you’re running solo, stick to routes that keep you close to your starting point—or have a backup plan in case the heat gets the better of you.

Don’t get discouraged by slower summer miles. They’re building the fitness that often leads to fall PRs.