When people move to a new area, they may have less problems with their asthma. This is called the honeymoon phase, which may last up to one year. After the honeymoon phase, your husband may start to have problems with his asthma again. Instead of moving, we recommend that people with asthma learn what triggers their asthma. Since asthma triggers vary from person to person, this is something that needs to be done on an individual basis. Then you and your husband can focus on finding ways to decrease or keep him from being exposed to those things. Please read our What Makes Asthma Worse MedFact at http://www.nationaljewish.org/medfacts/worse.html for more detailed information.
In general, many folks find a milder climate (not TOO hot, not too cold--just right--like the 3 bears) is helpful, as well as drier rather than humid.
Does he have allergies and allergic asthma? Does he appear to be better when he's in different climates? A prolonged visit to anywhere you are considering living may be useful in helping you decide. Best of luck!
Aloha,
Starion