Low mileage day

Mileage ran today: 3.25 miles with a couple of walk breaks inserted. I was slightly out of breath at mile 1.10 then tackled a hill (which was about 1/4 mile up) after my first walk break. Not sure what the problem was this morning but the weather was absolutely great(my favorite ,overcast and slightly breezy with low 70s temps). I look forward to running in cold weather, maybe it will help my breathing. Any advice would be greatly appreciated!!