You might find it hard to breathe when it's either too warm and humid or too cold and you aren't alone. According to a blog post that Dr. Oz penned for The Huffington Post, cold air causes small cracks to form in the lining of your bronchial tubes, which makes it hard and painful to breathe.And when it's hot and humid outside, the air can feel heavier, which makes breathing taxing. Add pollution to that and it gets even more difficult. According to the American Lung Association, this is especially true for those who have pre-existing lung conditions.