Title says it all…
DarkSky Weather works well but it seems to only be able to pull in the pressure value as mb (millibars). The value is then shown with the unit inHg (inches of mercury) since I’m using imperial units.
The rest of the values …
(I’m replying to this 7-month-old issue as that is the latest report of what seems to be a long-standing and ongoing bug. Search for “inHg” to see what I mean.)
I don’t know that this is a bug in DarkSky - it shows up in my HA which uses met.no, and it even shows up in the example screen for the Weather Forecast Card! see https://www.home-assistant.io/lovelace/weather-forecast/
Did no one notice that the pressure was shown as 1025 inches of mercury?! That’s like at the bottom of a thousand-foot-deep lake! 
So I’m guessing the bug runs deeper than DarkSky. Just a guess, tho, I’m struggling to understand the code…
Someone seems to have fixed the bug in the above example - it now shows 30-some inches of mercury - but on my fresh install it’s still mislabeled. Wow.