Now that is an interesting question, isn't it?
It started when i lived in a small place outsite this city.. after moving from a place that was so bad, very humid and moist. Because of faulty building process, and it was situated 50% below ground. So while i lived there, i bought a dehumidifier. It worked well, and then i started reading the % on the machine.
So i moved from there because it was so shitty place to live. The new place (old really ^^) was also humid. 80% ... the dehumidifer worked well there too, and it didn't -stay- humid like the other place.
But then it was like, okay i didn't have to use it all the time, so i bought a temperature+hygrometer instead. This was about 10 years ago. Since then i've kept an eye on it, followed the weather of the years and humidity as you mentioned. But also because i am an earth sun, water moon, you know, like the swamp thing, i've always felt that, when there is dry air outside, it gets dry inside, and then you feel like your body starts to dry out. This, at least to me, causes a kind of survival/desperation mode in the body and mind, drinking water becomes more vital, but also, eating food types that are more hydrating, like stews, is maybe more vital. Food types that keeps giving your body moisture from inside. I read every year about people getting problems from the dry air during winter+spring. And i've written this in some comment sections. Yet see very little good n practical advice from scientists. They are stupid.
Well, back to your question.
Most of winter here in Norway is dry. Very dry. It can get as low as constantly below 10% relative humidity in my place. Which is why i bought that water heater thingi wrote about here on jsp some 1 year ago.
And it's really bad. When sleeping, you snore more, since the mucus dries out. You feel dry all the time. It's good for drying clothes indoors, and to keep moisture away, which can be good for many things. Not get mold n such. But when it's that low, obviously it can dry out the skin, eyes, nose, you get sores easier. Using moisturizing cream n such becomes a thing. BUT! Most importantly, get that dang restaurant style water heater. It works extremely effective.
Winter+spring is usually very dry. Now, since about mid-May, it started increasing to more acceptable levels. 30-40%. And now, the last 2-3 weeks, 40-50%. Which will probably last until early winter, like october-november, when it drops again.
That's southeast of Norway. Been quite regularly like that for the 10 years i've been measuring.
So i really recommend buying one of those, thermo+hygrometer. Start following that. If it's too dry, you dry out. Too moist, you breathe heavy and get sleepy. About 38% is the best spot for me. 35-40%.
I know what you mean about food. Soup is core winter foods. Heats you up, moisturizes you from the inside out, it's hearty. Summer though it'll make me feel more full (over hydrated?) And just really warm since im a natural furnace.
My skin is very powerful though and makes alot of moisture. So I never have to moisturize or use Vaseline in the dry dry summer, I just feel okay. Lots of sweat perhaps. But in the winter I'll need to Vaseline my hands and moisturize my face or else it'll get red and itchy, dry, crack at worse. But thats decently high humidity id say. Our summer humidity right now on a 36 C hot day is about 30 percent, high enough for me. Dunno what it is in the winter but low