Like I said, it depends on how your house was constructed. If your house has a vapor barrier on the inside, then the vapor barrier should be above the dew point and water should not condense regardless of humidity level in your house.

The problem is not all houses are built that way. Many older houses don't have a vapor barrier. And in some cases the vapor barrier is on the exterior of the wall.

This is actually mandatory in hotter, wetter, climates with air conditioning, as the AC causes the same problem but in reverse: if the vapor barrier is on the inside, the vapor barrier is on the cold side, and water from hot and humid outside air will condense.

There isn't necessarily any one solution to this. In places like Toronto in summer you have very hot and humid weather – with lots of air conditioning – while also having very cold winters. Regardless of where the vapor barrier goes you're screwed in certain conditions. So it's common to use different technologies like vapor retarders to try to let wet parts of the wall eventually dry out. But they inherently are vulnerable to abuse, like people trying to maintain a high humidity in winter.