Cold air that gets into your lungs can make it hard to breathe and I've experienced it myself.
When I have to be outside in the frigid temperatures like 18 F which is what the temp is right now outside then I have to wear a scarf over my mouth if I'm out longer than 30 minutes.
Also if you're straining yourself as well doing work then it will be even harder to breathe.
If you have to work outside in the cold weather it's best to take breaks every 30 to 40 minutes and go inside somewhere warm.
The cold air outside is also dry air which also irritates your lungs especially if you already have lung conditions or other breathing problems.
Also besides causing shortness of breath the cold air can cause bronchial tightening or constriction leading to coughing and wheezing.