Winter makes asthma worse and can raise the potency of other trigger factors. This means that things which you’d plan for, which otherwise wouldn’t touch you will be more damaging and could overwhelm whatever preparations you’ve prepared. The winter’s cold air is damaging in itself and has the potential of sparking its own asthma attack at worse and respiratory symptoms are best, these can include wheezing and breathlessness.
The colder times of the year bring with them all sorts of bugs and infections which can clog the airways and otherwise leave an asthmatic more exposed to an asthma attack. Adversely, being out of the cold and in a central heated home can be just as bad for you as an asthmatic as the air quality is generally worse. Cranking up the heating will make the air drier and worse for your lungs; also closing all doors and windows prevents fresh air from circulating which also degrades the quality of air available.
The best thing you can do to counter this time of year on the whole is to speak to your doctor and then work with them on a plan of action should the weather get the better of you. As long as you’re prepared you shouldn’t be in any danger and you should be free to live your life as you otherwise would.