Post #904: Dryer air arrives in Virginia

Posted on December 2, 2020

Source:  National weather service (, downloaded 12/2/2020.

I’ve been tracking the relative humidity in my house for roughly the past month.  November had relatively few days with truly dry outdoor air.  Air that was both cold, and had low relative humidity.

Unsurprisingly, I’ve had to run my indoor humidifier infrequently, so far this year.

Today, and looking forward to the forecast for the next two weeks, that appears to be changing.

As shown above, today is cool and dry.  That 31% outdoor relative humidity (at 47F) would result in a roughly 15% indoor relative humidity at 68F, absent any other inputs of water vapor into the indoor air.  Today my humidifier is running constantly but my indoor humidity is slowly dropping anyway.

For the next two weeks, it looks like a typical day will be 45F with 55% outdoor relative humidity.  Absent any other inputs, those conditions will translate to an indoor relative humidity of 25% at 68F.  That’s a long enough period that houses and other indoor locations should be fairly well dried out by the end of it.  Absent a humidifier, indoor air in this region will be quite dry by mid-December.

If you wonder why I’m tracking this, refer to Post #894.  I heard from a few readers who purchased humidifiers after reading that.  If you have one, but haven’t unboxed it and set it up, now would be a good time to do that, I think.