Find your climate
| Climate | Target | Where |
|---|---|---|
| Hot and humid | 45–55% | Florida, Louisiana, coastal Texas, Georgia, the Carolinas, coastal Alabama and Mississippi |
| Hot and dry | 30–40% | Arizona, Nevada, inland Southern California, New Mexico, west Texas |
| Cold winters | 30–40% | Minnesota, Wisconsin, Michigan, Illinois, New York, New England, Colorado, Montana |
| Mild and damp | 40–50% | Western Washington and Oregon, coastal Northern California, coastal British Columbia |
| Four seasons | 30–50%, seasonal | Virginia, Maryland, Delaware, Kentucky, Tennessee, Missouri, southern Ohio and Indiana |
Hot and humid
Florida, the Gulf Coast, the Southeast. Outdoor air carries more moisture than your indoor air for months at a time.
Hot and dry
Phoenix, Las Vegas, Albuquerque. Almost every month is a dry-air problem — with a short, sharp exception.
Cold winters
Upper Midwest, Northeast, Mountain West. The target is not one number — it falls with the outdoor temperature.
Mild and damp
Seattle, Portland, the coast. Nothing is extreme and everything is damp — the hardest climate to notice a problem in.
Four seasons
Mid-Atlantic, Ohio Valley, Tennessee Valley. Dehumidifying in July, humidifying in January, in the same house.
Why one number cannot serve every house
The 30–50% band is a national average of a moving target. What actually decides your number is the temperature of your coldest surface and the moisture content of the air outside — and both of those are climate, not preference.
In a cold climate the winter target has to fall as the outdoor temperature does, or the windows run with water. In a hot-humid climate 40% is technically achievable and financially foolish. In the desert, 50% is a fight against physics. Pick the page that matches your weather rather than the average of everyone else's.