About Barometer Now & Our Data Sources

Barometer Now shows live barometric pressure from official weather stations, the elevation of any spot on Earth, and simple tools for pressure units and altitude. It is free, needs no account and is made by Appcellent.

Where the pressure comes from

Live pressure comes from METAR reports — the hourly observations airports publish for pilots — through the NOAA Aviation Weather Center. The number we show is the altimeter setting: the station’s measured pressure reduced to sea level. That is the figure weather reports, forecasts and most weather apps call “pressure”, and it lets you compare places at different elevations.

Each of the 185 city pages uses the closest reliable station, usually the main airport. The home page picks the station nearest to your approximate location (from your IP address, handled by our host Cloudflare), or your exact location if you press “Use my exact location”. Data is refreshed about every 10 minutes. The 3-hour trend compares the latest report with the one closest to three hours earlier and uses the standard forecasting terms (steady, slowly, quickly, very rapidly).

Elevation and places

City coordinates, time zones and elevations for 200 places come from GeoNames (CC BY 4.0). The elevation finder reads Mapzen Terrain Tiles on AWS, built from USGS 3DEP, SRTM and other open elevation data.

Calculations

Standard pressure at an elevation: the International Standard Atmosphere (1013.25 hPa and 15 °C at sea level).
Station (absolute) pressure from the altimeter setting: the NOAA/NWS altimeter equation.
Boiling point of water: the Clausius–Clapeyron relation.
Pressure and density altitude: the standard-atmosphere equations used in aviation.

Limits

Readings are for information. Stations can go offline or report late, and a city’s weather can differ from its airport’s. Do not use this site for flight planning or safety decisions — use official sources such as your national weather service and aviation briefings.

Contact

Questions or a city you would like added: support@barometernow.com.