When i was 18 I worked for a 1 legged man named Woody at a Bait Store in Abilene Texas and he showed me how to make a Barometer with a 1 quart glass Mayonaise Jar and a tall Glass Coka-Cola bottle and he swore by it and I do to because it is VERY Accurate.
Fill the 1 Quart Mayo jar and fill it with water.
Stand the Coke bottle upside down in the CENTER inside of the Mayo jar.

The water will start goin up insde the Coke Bottle as the Barometric Pressure rises .....
This is when the fish are Biting is what he always said....
He was a FlatHead Trotline Fisherman Only....