Is it too cold to exercise outside?

Is it too cold to go and and ride? Articles in both the St. Louis Post-Dispatch and the Springfield News-Leader say no:
"Don't be deterred to run just because it's cold," said Dave Watt, executive director of the American Running Association. "Just use some common sense."

Experts say that with the right clothing and sound judgment, it's OK to keep running outside even at 20 below. But they also tell runners to know their personal limits.
IceBike.com has really good bicycle-specific advice for getting out the in cold.