It seems far-fetched to think of a gauge on your wall that can tell you when it's a good time to hunt, but a barometer does exactly that. It measures the changing weight of air, or atmospheric pressure. Cold, dry air registers higher readings on the barometer than warm, wet air. So, large air masses of cold, dry air are called highs, and masses of warm, moist air are called lows. Highs, or high readings on the barometer, are associated with fair weather. Lows, or low readings on the barometer, are associated with stormy weather. Falling barometric pressure can indicate that a storm is coming in even before nice weather starts to turn nasty.