Barometric pressure today

How to read the chart and the swing

The curve shows sea-level pressure from a day ago through now and 72 hours ahead. A single value on it says little; the slope says more. So under the chart you get two figures: how much pressure changed over the past 24 hours, and the biggest change over any 24 hours expected in the next three days.

We label the swing on a rough scale, the same one used on the MeteoHealth landing page: under 3 hPa is small, 3 to 6 is noticeable, 6 or more is large. It is our working scale for reading the chart, not a medical threshold. The studies we cover do not use it, so please do not draw conclusions about yourself from it.

A forecast is still a forecast. By day two or three it can be off by a fair margin, and tomorrow evening's curve may shift by morning.

Barometric pressure today: why you see two numbers, and why your city's forecast differs

We show pressure two ways. "Sea level" is pressure converted as if your spot sat at 0 m elevation. Weather services draw it on their maps, and the MeteoHealth landing page uses it. "At the surface" is the actual pressure at your city's elevation, which many local forecasts show, often in mmHg.

The higher the city, the lower the second number: at the surface, pressure drops by roughly 1 hPa for every 8 metres of elevation. Standard sea-level pressure is 1013.25 hPa, which is 760 mmHg (1 hPa is about 0.75 mmHg). So a mountain town has a very different "normal", and comparing your number with someone else's tells you little.

The key point: the 24-hour change is almost the same in both series. When your city's forecast and our chart disagree on the absolute number, it is usually two ways of measuring, not an error. For how you feel, the change is what to watch.

What a pressure swing can and cannot tell you about how you feel

In a diary study of 34 Japanese migraine patients, attacks clustered when pressure had fallen to roughly 1003–1007 hPa, about 6 to 10 hPa below the standard 1013 (Okuma et al., 2015). But the evidence overall is mixed and the response is highly individual: some people show a clear link to pressure, others show none. More in our article on barometric pressure and headache and our review of what the science says about weather sensitivity.

A chart cannot tell you how you will feel. It can hint at when it may be worth paying closer attention, but it does not say what will happen. Temperature changes the picture too: see sudden temperature changes.