Barometric Pressure
Barometric pressure is the force that is exerted on objects by the weight of the atmosphere above them. Generally speaking, as elevation increases, there is less atmospheric mass, so the barometric pressure decreases.
How to find barometric pressure:
Step 1:
Look up the barometric pressure for your site using this website http://www.localconditions.com. Type in a city that is close to your site and click "Go". Record the barometer reading (in Hg).

Step 2:
This barometric pressure must be corrected for elevation and temperature. Use this website http://www.csgnetwork.com/barcorrectthcalc.html to calculate the corrected barometric pressure. Enter the air temperature, elevation of barometer, and the barometric pressure that you just looked up. The calculator will then give you the corrected barometric pressure.
Circled = parameters I filled in given the information gathered in step 1.
Rectangle = actual barometer corrected, given after I filled out the circled information

Step 3:
Multiply the corrected barometric pressure value by 25.4 to convert Hg to mmHg. This is the value you record.

22.89 X 25.4 = 581.406 