Air Pressure Explained: Highs, Lows, and Weather Changes

Atmospheric pressure is the weight of air molecules pressing down on every surface. Sea-level average is about 1013 hPa (hectopascals), 29.92 inHg, or 760 mmHg. Pressure changes with altitude, temperature, and weather systems — low-pressure zones draw air inward and upward (clouds, storms); high-pressure zones sink air (often clearer, calmer).

Units and conversions

Meteorologists use hPa (millibars) globally; US barometers often show inHg. Aviation and some lab work reference mmHg. The Atmospheric Pressure Calculator converts between units and estimates pressure at elevation using standard atmosphere models.

• 1 inHg ≈ 33.86 hPa
• 1 atm = 1013.25 hPa
• Pressure drops ~1 inHg per 1000 ft climb (rough guide)

Reading a barometer trend

Absolute value matters less than change rate. Rapid fall (>0.06 inHg / 3 h): storm approaching. Steady rise: improving conditions. Stale high pressure in summer: heat; in winter: cold dry outbreaks. Combine with wind and satellite — pressure alone is not full forecast.

Pressure and your body

Ear popping in aircraft or mountains reflects rapid pressure change across eardrum. Weather-sensitive individuals report joint pain with falling pressure — mechanism debated but widely reported. Cooking times shift slightly at high altitude because lower boiling point of water follows lower pressure.

Frequently asked questions