Basics
What Is Normal Barometric Pressure?
Normal sea-level pressure is 29.92 inHg (1013.25 hPa). Here are the ranges for high, low and extreme readings, and why the normal at your elevation is lower.
Normal barometric pressure is 29.92 inHg (1013.25 hPa or mb) at sea level. Readings between about 29.80 and 30.20 inHg (1009–1023 hPa) are normal; above that is high pressure, below it is low pressure.
High, normal and low at a glance
| Sea-level pressure | inHg | hPa / mb | Typical weather |
|---|---|---|---|
| Very high | above 30.50 | above 1033 | Cold, dry, very clear |
| High | 30.20–30.50 | 1023–1033 | Fair, settled, light winds |
| Normal | 29.80–30.20 | 1009–1023 | Changeable |
| Low | 29.50–29.80 | 999–1009 | Cloudy, breezy, showers |
| Very low | below 29.50 | below 999 | Storms, strong winds |
These bands are rules of thumb for mid-latitudes. In the tropics pressure varies much less from day to day, so a reading of 1005 hPa there can be more meaningful than it would be in Chicago.
Why 29.92?
29.92 inHg (1013.25 hPa) is the average sea-level pressure of the International Standard Atmosphere, the reference model used in aviation and engineering. It is a convention, not a target: real pressure is almost never exactly 29.92.
Records
- Highest sea-level pressure on record: about 1084 hPa (32.01 inHg), Agata, Siberia, December 1968.
- Lowest (outside tornadoes): 870 hPa (25.69 inHg) in the eye of Typhoon Tip, October 1979.
- In the US, readings above 31.00 inHg (1050 hPa) occur in the strongest Arctic outbreaks over the northern Plains.
Normal at your elevation
The forecast’s “normal” is a sea-level number everywhere. But a barometer that is not corrected to sea level reads less the higher you are:
| Elevation | Normal absolute pressure |
|---|---|
| Sea level | 29.92 inHg · 1013 hPa |
| 1,000 ft | 28.86 inHg · 977 hPa |
| 2,500 ft | 27.32 inHg · 925 hPa |
| 5,000 ft | 24.90 inHg · 843 hPa |
| 7,500 ft | 22.65 inHg · 767 hPa |
| 10,000 ft | 20.58 inHg · 697 hPa |
Find your own elevation with What is my elevation?, or look up a city on the elevation list.
The trend matters more than the number
A reading of 29.85 inHg tells you little on its own. Whether it got there by rising from 29.60 or falling from 30.10 tells you a lot. Check the 3-hour change next to the live reading: falling more than 0.05 inHg (1.6 hPa) in three hours means weather is on the way. See how to read a barometer.