03/16/2026
I get a LOT of phone calls in weather like we are having in South Dakota right now from people who think they have windows that need replacement. They all say they have ice and water on their windows, a lot of cases there is visible mold at the bottom corners. In pretty much 99.9% of the cases the problem is interior humidity. This chart shows what humidity levels in a home should be at various outdoor ambient temperatures in the upper midwest. With our part of the world being an extremely humid climate maintaining low enough humidity to prevent condensation and mold is always a problem. In most cases I find very high indoor humidity readings plus humidifiers running to make the problem worse. So, to resolve these issues the recommendation would be, if you own a humidifier take it directly to the garbage can, and in the summer months run the central air and a dehumidifier and regularly check the relative humidity in your home. In this type of climate finding humidity is not the problem, the problem is maintaining it at a low enough level.
