It's too darn cold ... the footing is too slick ... too much crusty snow on the sidewalk ... your nose turns red and starts running faster than you are ... and, besides, your lungs can freeze, right?
Well, not exactly. But a person who has exercise-induced asthma can precipitate an asthma episode by running in cold, dry air, and perspiration-wicking clothing is a must.
So says the University of Washington's Dr. John O'Kane, a sports physician who serves as team doctor for Husky athletic teams.
"Overall, there's no reason that you have to stop your training in the winter," he says. "There are just some different considerations to keep in mind."
One of those is exercise-induced asthma, a condition the runner may not even be aware of.
"Some runners may find they can run in the summer without problems, but if they run in winter they may cough or wheeze or have shortness of breath. If they're having those symptoms, they should talk to their doctors, because there may be simple remedies that will allow them to continue training."
O'Kane makes these suggestions for cold-weather runners:
"People think when you're running you're going to be hot," O'Kane says. "But if you get wet, you lose body heat quickly and run the risk of hypothermia, particularly if you're going on a long run."
"The days are shorter in winter; you may be running in the dark," O'Kane says. "You have to be wearing something bright or reflective, and you really have to watch out for cars.
"Really, without question, the highest risk for someone who's road-running is being hit by an automobile."