Texas · 203 m elevation

Barometric Pressure in San Antonio, TX

• 30.00Average pressure (inHg, sea level)
• 125.9Swing days a year · 36th of 50
• 49.3Big-swing days a year (≥10 hPa)
• 64.4Significant 24h drop days a year

Overview

San Antonio averages 125.9 significant pressure swing days a year — but 21.7 fall in January and just 0.2 in July. Records, seasonal data, and rankings.

San Antonio's sea-level pressure averaged 30.00 inHg (1016.0 hPa) across 87,672 hours from 2015 through 2024, with a median of 29.98 inHg (1015.2 hPa). Most of the time the barometer stays in a narrow band: the 5th-to-95th percentile range runs from 29.75 inHg (1007.3 hPa) to 30.34 inHg (1027.5 hPa), and the standard deviation is 0.18 inHg (6.04 hPa) — below the 50-city median of 0.20 inHg (6.87 hPa).

At 203 meters of elevation, San Antonio's station pressure sits well below those sea-level figures. Mean surface pressure is 29.31 inHg (992.4 hPa), about 0.70 inHg (23.6 hPa) under the mean MSL value. A home barometer that hasn't been calibrated to sea level will read near 29.31 inHg on an ordinary day, not 30.00 — that offset is elevation, not a malfunction.

Nationally, San Antonio lands in the calmer third: #36 of 50 for significant swing days, #35 for big-swing days, #35 for pressure variability, and #44 for its largest single 24-hour drop. It logs 125.9 significant swing days per year against a national median of 180.7, and 49.3 big-swing days against a median of 86.1. But that annual average conceals two very different regimes, and reading it as "steady year-round" would be a mistake.

Migraine & pressure-sensitivity outlook

• Low — under 6 hPa (0.18 inHg)
• Elevated — 6 to 10 hPa
• High — 10 hPa (0.30 inHg) or more
• Dashed outline = forecast (after today)

Association only. This calendar shows days when pressure changed — or is forecast to change — sharply over 24 hours, conditions associated with pressure sensitivity in some people. It is not a prediction of symptoms, not a diagnosis, and not medical advice. The 30 days of history are there so you can compare the days you actually felt something against what the barometer did. Talk to a clinician about headache or migraine management.

On a typical day the barometer barely moves — the median absolute 24-hour change is 0.07 inHg (2.3 hPa). The 95th percentile is 0.30 inHg (10.2 hPa), which is exactly the big-swing threshold, so roughly one day in twenty brings a change of that size. Over a year that works out to 125.9 days crossing the 0.18 inHg (6 hPa) significant-swing line, 49.3 crossing 0.30 inHg (10 hPa), and 64.4 significant 24-hour falls — the direction many pressure-sensitive people report as the more noticeable one. Shorter intervals stay gentle: the 5th percentile 6-hour change is -0.14 inHg (-4.6 hPa), and the steepest 6-hour fall in ten years was -0.28 inHg (-9.5 hPa).

Those days are not spread evenly. Drop days run 11.6 in January and 11.4 in February, versus 0.1 in July and 0.2 in August. November through March accounts for the large majority of the year's significant swings, and all five of the ten-year record drops occurred in that window. In practical terms, San Antonio offers a long quiet stretch from roughly June through September, then a concentrated cool season that delivers the conditions many pressure-sensitive people report as triggers — including sharp rises, not just falls.

For comparison: Denver logs 281.6 swing days a year, 2.24 times San Antonio's total, and 169.8 big-swing days versus 49.3 here — 3.4 times as many. Colorado Springs runs 3.5 times San Antonio's big-swing count. At the other end, Miami sees just 19.8 swing days a year, so San Antonio has about 6.4 times Miami's. Among Texas cities, San Antonio sits close to Austin (132.0 swing days, essentially the same regime) and quieter than Fort Worth (163.0) and Dallas (155.1), while Houston, at 107.3, is the calmest of the group.

Seasonal patterns

The split is stark. January produces 21.7 significant swing days; July produces 0.2. February runs 20.2, December 17.9, March 17.6 — while June logs 1.5, August 0.6, and September 1.9. Monthly variability tracks the same curve: January's standard deviation is 0.22 inHg (7.4 hPa), above the 50-city median for a full year's variability, while July's is 0.08 inHg (2.61 hPa), about as flat as any month in the dataset. In summer the subtropical ridge sits over South Texas and erases the pressure gradient. From late fall into early spring, cold fronts driving down the Texas plains restore it.

Mean pressure follows the same rhythm, peaking in January at 30.15 inHg (1020.9 hPa) and December at 30.10 inHg (1019.4 hPa), then bottoming in May at 29.90 inHg (1012.4 hPa) and June at 29.91 inHg (1012.7 hPa). July recovers slightly to 29.96 inHg (1014.7 hPa) as the ridge builds.

The extremes are all cool-season. The record high of 30.81 inHg (1043.5 hPa) came on December 23, 2022; the record low of 29.31 inHg (992.6 hPa) on March 2, 2023 — a full range of 1.50 inHg (50.9 hPa) over ten years. The five sharpest 24-hour falls were -0.59 inHg (-20.0 hPa) ending January 8, 2024; -0.52 inHg (-17.7 hPa) on December 31, 2016; -0.51 inHg (-17.4 hPa) on November 28, 2016 and again on March 21, 2022; and -0.47 inHg (-16.0 hPa) on March 24, 2024. Every one fell between November and March. One local signature worth noting: the largest 24-hour rise on record, 0.80 inHg (27.2 hPa), is 36 percent bigger than the largest fall. The post-frontal cold surge behind a Norther moves this barometer harder than the pre-frontal drop does.

Month by month

Swing days: 24-hour change of at least 6 hPa (0.18 inHg). Drop days: 24-hour fall of at least 6 hPa. Averages per year, 2015–2024.

Records and extremes

Sharpest 24-hour drops, 2015–2024

Nearby cities

• Austin, TX
• Houston, TX
• Fort Worth, TX
• Dallas, TX
• Oklahoma City, OK
• Tulsa, OK

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