The cold and slushy winter weather that's headed for the region will also impact runners in the Marine Corps Marathon on Sunday.
Participants in the marathon and 10-K race are bracing for freezing temperatures.
Deidre Douglas was nursing an old injury Friday, but her knees won't be the only pain point during the race.
"I'm a little nervous," Douglas said, but she's confident the cold weather won't throw her off her path. "I can take the cold, because you have clothes on. Gets too hot and there's only so much you can take off before it starts to become a problem."
Now runners are trying to put more clothes on, with hats, gloves and long-sleeve shirts selling quickly at the Marathon's health and fitness expo.
"We actually have been spending the last week or so shopping for clothes to wear during the first hour of the race," one runner said.
Ray Pugsley, who owns the Potomac River running company, says it's important runners get to the start overdressed Sunday.
"Often times, people will get into a marathon and they'll feel at 15 miles, they'll feel like they normally do at 21, 22 miles and they can't figure out why," he said. "Oftentimes you can tie it back to standing around shivering for an hour and a half beforehand."
Runners who aren't used to the cold weather can expect to feel the pain. Marathon trainer Michael Moses says joints such as knees need to be covered when it's cool to keep circulation up.
"I have outside knee tendentious and when they get cold, I'm in pain. That will stop you from running a marathon," he said.
Sunday's marathon and 10-K race will shut down roads from the Pentagon through the District.