Hind Sight is 2020

Around 1990, I was the primary software developer for a business that designed and manufactured computerized greenhouse controls -- basically, sensors communicated with a PC which used those inputs to command controllers for lights, windows, fans, heaters, etc. You learn a few things while working such projects.When we talk about humidity, it's relative humidity, which is affected by several factors not just the amount of water vapor in the air (this became very apparent when I first saw a psychrometric chart). For a given amount of water vapor in a given volume of air, temperature is a major factor in changing relative humidity with higher temperatures lowering humidity.So when humidity in the greenhouse is getting too high, the first action is usually to open the vents to draw in fresh air, but if the outside air is even more humid then that's not done. The second action is to turn up the heat (though for certain plants there are limits to that too), which drives the humidity down. Our software also stored sensor data and print it out in graphs. We could see how humidity was rising and then was held in check by turning up the heat (temperature also being graphed).When I was stationed in north-eastern North Dakota (the cold part of the state) a couple decades earlier, I saw the opposite side at work. Because of the low temperatures in the dead of winter (mostly from arctic air masses descending upon us from Canada), the air could not hold much water vapor -- when we arrived in the summer we were told that it would get too cold to snow and we foolishly thought they were joking. All the snowing was when it was warm (higher than -10°F) such as in the beginning and at the end of winter. But then when that cold outdoor air came indoors and heated up by the furnace, the humidity dropped even more radically making for fierce static electricity and dried out skin. A common attachment on furnaces was a humidifier to make indoor air more comfortable.