Is it bad for your body to run outside in cold weather when you're not bundled up? I ran this morning w/ shorts and a t-shirt and it was cold. My knees were hurting afterward.
The experts say to wear enough running clothes to make you feel just a bit of cold when you step out the door. You don't want to walk out the door and already feel warm because you'll heat up so much on your run and be uncomfortably hot. I wouldn't say it's necessarily bad for the body to run outside in cold weather in so far as I doubt there are long term side effects. In the short term yes, you're likely to get a bit stiff and sore.
I myself loath running in pants and do anything I can to stay out of them, but when winter calls, I do dig out my supply of tights. I have a great pair of capri tights that I prefer to their full length counterparts. I also dress in layers up top so I can strip off a long sleeve shirt if I need to.