We’ve had an unusually cold winter this year. Now, as someone who grew up with cold winters, you’d think I’d be okay with this. But I’ve had ten fairly “warm” winters in four different cities. You kind of get used to that. To be honest, the cold isn’t horrible (except in how it shows itself in my heating bill); it’s just that I know what my city’s winters are usually like.* By mid-March two years ago, my friends and I were patio-ing our beer.** I want that kind of a winter.
Instead we’ve had a barely double digits winter (except at the weekend when it was 60F/14C). And as soon as I step outside, my nose starts running. I obviously know that this is the normal reaction and probably a sign that my body’s doing something it’s supposed to, but I don’t know why.
Short answer: your nose runs because cold air is very dry.
Long answer: your nose runs because cold air is very dry and the purpose of your nose is to make the air you breathe warm and wet for your lungs.*** In order to provide the moisture your lungs need to be happy in the cold, your nose has to produce extra fluid. The result of this is that your nose starts to run. To add to the problem, what you see when you see your breath is moisture and when you exhale through your mouth, that water recondenses and some of it (obviously, one feels) ends up on your nose.
For more information, see here.
*In fairness, this whinging would probably annoy a friend who lives in a particularly northern city in my homeland. Then again, he’s currently spending a week in El Salvador, so I don’t have that much sympathy for him.
**And, as previously noted, everyone knows that outdoor beers always taste better than indoor beers. That’s a fact.
***Tangentially, this also explains why when it’s very, very cold out (for those of you who have never had the pleasure of stepping outside when it’s -40) it physically hurts to breathe.