It always seems to be way off, like this:

any idea why? (It's anything but Fair now)

A barometer is used to forecast approaching weather. It is not a representation of your current conditions. Check out the following link for more information:

http://www.bom.gov.au/info/aneroid/aneroid.shtml

"approaching weather" - hanson's current conditions are rain, the evening conditions are forecasted to be rain and the next day's forecast is rain, so the barometer is forecasting the weather when, two days out, three?

Basically at some point in time all current weather conditions are going to end and it will be Fair. So the barometer can always indicate Fair and always be right.

And this is a perfect example of why a barometer is worthless IMO.

I do agree with Ed. In this case it's forecasting fair weather ahead 7 days. lol Rain yesterday, and the next clear 'Fair' day is Thursday.