What Do Barometric Pressure Numbers Mean?

Tools

By By Steve Pool

SEATTLE - A barometer measures atmospheric pressure, which can help give you a rough idea of how the weather will be changing in the next 24 hours.

Sea-level barometer readings usually range from about 29.70 inches of mercury to 30.20 or so, with 29.92 being the average reading.

Pressure also drops with altitude too, so reported pressures are converted to sea-level to factor out the difference in altitude from individual reports. You can convert your observed pressure to sea-level by subtracting .06 inches for every 50 feet in altitude.

But it's not so much the actual number reading as the trend the readings are taking. A steadily falling barometer usually signals a storm is approaching, while a rising barometer normally means sunnier skies ahead. Although very low readings (under 29.50 inches) can suggest a strong storm approaching.

Your Photos

YouNews Up! Up! And away! Up! Up! And away!
When I saw this dramatic cloud to the north, it reminded me of smoke, rising in billows until it hits the jet stream, then it's pulled hundreds of miles east. I had to capture it quickly. Within minutes the effect had faded.
YouNews Inside an osprey nest Inside an osprey nest
For my girlfriends birthday we had a party at her parents. We knew the nest was there but the owner hadn't seen or heard the osprey for a day or two. He asked me to fly my drone up and see if any was wrong. I flew up and found that there were two eggs inside.
YouNews Our Garden Our Garden
The growing season has been great.

The secret to this garden is simple.
I used recycled grass clippings.