Reference
barometric pressure.
The number at the bottom of your weather app, translated. Every reading from 28.50 to 30.99 inHg and 965 to 1045 hPa gets its own page — what it means, what it means rising, steady and falling, and what it converts to on every other scale.
start here
If you are looking up a number you just saw on your phone, jump straight to it below. If you want the physics first, read barometric pressure explained.
the eight bands
Pressure is continuous, but meteorologists read it in bands, because the difference between 29.85 and 29.86 is nothing and the difference between 29.5 and 30.2 is a change of regime.
below 28.50 inHg
below 965 hPa
Extreme low — hurricane-core pressure
Sustained hurricane-force wind, torrential rain, and — on any coast — storm surge. In an extratropical case, a rapidly deepening cyclone with widespread damaging gusts and, in winter, blizzard conditions on its cold flank.
28.50 – 28.99 inHg
965 – 981 hPa
Very low — deep-storm pressure
Heavy, persistent precipitation and strong wind across a broad footprint. On the US East Coast this is classic nor easter territory; in the Gulf and Atlantic it is a landfalling tropical system; in the Midwest it can be an inland cyclone strong enough to produce a wind event without a thunderstorm.
29.00 – 29.49 inHg
982 – 998 hPa
Low — an organized storm system
Steady rain or snow, overcast skies, and a noticeable wind. Frontal passages are common at this pressure — a wind shift, a temperature change, and a band of heavier precipitation moving through.
29.50 – 29.79 inHg
999 – 1008 hPa
Below normal — unsettled weather
Clouds, showers, and the kind of gray, changeable day that a forecast summary struggles to describe. Frontal boundaries and the outer circulation of distant lows both live in this range.
29.80 – 30.05 inHg
1009 – 1017 hPa
Normal — ordinary sea-level pressure
Almost anything. Clear, cloudy, light rain and dry-and-mild are all consistent with a reading in this band, which is exactly why reading the number without the trend is a waste of the number.
30.06 – 30.35 inHg
1018 – 1027 hPa
Above normal — fair-weather high pressure
Clear or mostly clear skies, light wind, and stable air. In summer this produces hot, hazy afternoons; in winter, cold nights with strong radiational cooling and the risk of frost or fog by morning.
30.36 – 30.69 inHg
1028 – 1039 hPa
High — a strong high-pressure system
Cold, dry, and strikingly clear. Winter highs at this pressure produce the deepest overnight cold, sharp visibility, and often a marked temperature inversion near the ground.
30.70 inHg and above
1040 hPa and above
Very high — an exceptional high-pressure event
Bitter cold, bone-dry air, and near-perfect clarity. Strong low-level inversions are common, which can trap whatever pollution exists near the surface even as the sky overhead stays flawless.
every reading — inches of mercury
250 readings, 28.50 through 30.99 inHg. This is the scale US weather apps default to.
every reading — hectopascals
81 readings, 965 through 1045 hPa. Identical to millibars, and the scale used by most of the world’s weather services — 1013 hPa is 29.91 inHg.
What does the barometric pressure on my weather app mean?
Barometric pressure is the weight of the atmosphere above you, reported as a sea-level-adjusted value in inches of mercury (inHg) in the US or hectopascals (hPa) almost everywhere else. Standard is 29.92 inHg or 1013.25 hPa. Higher readings mean sinking, stable air and generally fair weather; lower readings mean rising air, cloud and precipitation. The reading alone is only half the signal — the direction it has moved over the last three hours is what actually forecasts your day.
Frequently Asked Questions
What is a normal barometric pressure reading?
Standard sea-level pressure is 29.92 inHg, or 1013.25 hPa — the reference value used to calibrate aircraft altimeters worldwide. In practice most days fall between 29.80 and 30.05 inHg (1009 to 1017 hPa), which is the band where the reading tells you almost nothing on its own and the trend tells you everything.
Is high or low barometric pressure better weather?
High pressure means sinking air, which warms and dries as it descends and suppresses the upward motion clouds need — so high generally means clear and settled. Low pressure means rising air, which cools and condenses — so low generally means cloud and precipitation. The useful signal is the direction of change: rising toward fair, falling toward unsettled.
How do I convert inHg to hPa?
Multiply inches of mercury by 33.8639 to get hectopascals, or multiply hectopascals by 0.02953 to get inches of mercury. Millibars (mb) are numerically identical to hectopascals, so 1013 hPa and 1013 mb are the same reading. Every page in this reference lists the same pressure in inHg, hPa, mb, mmHg and kPa.
How fast does pressure have to fall to mean a storm?
Weather services report tendency over three hours. A change under 0.02 inHg (0.7 hPa) in three hours is effectively steady. Around 0.03 inHg (1 hPa) is a real trend. A fall of 0.07 inHg (2.5 hPa) in three hours is rapid and signals a system organizing. A drop of 24 hPa in 24 hours is the formal threshold for explosive cyclogenesis — a bomb cyclone.
Does altitude change the barometric pressure my app shows?
No. Weather apps report sea-level-adjusted pressure — the value your station would read if it sat at sea level. Raw station pressure in Denver runs near 24.8 inHg simply because there is a mile less atmosphere overhead, so without the adjustment every mountain station would look like a permanent hurricane. If a home barometer reads well below your app, it is reporting station pressure and needs to be set to your elevation.
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