Barometric Pressure and Weather — What the Numbers Mean

What Is Barometric Pressure?

Barometric (atmospheric) pressure is the weight of the air column above you. It is measured in hectopascals (hPa) or millibars (mb) — they are the same unit. Standard sea-level pressure is 1013.25 hPa.

How Pressure Predicts Weather

• Rising pressure → air is sinking → clouds disperse → fair weather ahead
• Falling pressure → air is rising → clouds form → rain or storms likely
• Steady pressure → current conditions will persist

Reading the Numbers

Why Changes Matter More Than Absolutes

A reading of 1005 hPa can mean different things. What matters is the trend. If pressure dropped from 1020 to 1005 over 12 hours, a storm is approaching. If it has been steady at 1005, conditions are stable.

Pressure and Altitude

Pressure decreases with altitude. At 1,500m elevation, normal pressure might read only 845 hPa. Weather stations adjust readings to sea-level equivalents for comparison.

Practical Tips

• Check pressure trend arrows on weather apps, not just the current value
• Rapidly falling pressure (more than 5 hPa in 3 hours) warns of approaching severe weather
• Some people experience headaches when pressure drops quickly

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Track pressure changes on Weather Tomorrow.