California · 12 m elevation

Barometric Pressure in San Diego, CA

• 29.98Average pressure (inHg, sea level)
• 35.4Swing days a year · 49th of 50
• 5.3Big-swing days a year (≥10 hPa)
• 15.0Significant 24h drop days a year

Overview

San Diego has the 2nd-calmest barometer of 50 US cities — 35.4 significant swing days a year and a mean of 29.98 inHg (1015.2 hPa). Full 2015-2024 data.

Across ten years of hourly data (2015-2024), San Diego's mean sea-level pressure is 29.98 inHg (1015.2 hPa), with a median of 29.97 inHg (1014.8 hPa). The middle 90% of all hours falls between 29.82 inHg (1009.9 hPa) and 30.17 inHg (1021.6 hPa) — a band of about a third of an inch of mercury. The standard deviation is 0.11 inHg (3.64 hPa), which ranks 49th of 50 major US cities; only Miami's barometer is flatter. The day-to-day numbers say the same thing. A typical 24-hour change here is 0.04 inHg (1.5 hPa), and even at the 95th percentile, 24-hour movement reaches only 0.16 inHg (5.3 hPa) — below the 0.18 inHg (6 hPa) threshold that counts as a significant swing. Six-hour changes stay between -0.07 inHg (-2.4 hPa) and 0.06 inHg (2.2 hPa) 90% of the time.

At 12 meters of elevation, San Diego needs almost no correction. Station pressure averages 29.93 inHg (1013.7 hPa) against the sea-level mean of 29.98 inHg (1015.2 hPa) — a gap of 0.04 inHg (1.5 hPa). A home barometer reporting raw station pressure will read within a rounding error of official values, and most consumer units apply sea-level correction by default anyway.

For national context: San Diego logs 35.4 significant swing days per year against a national median of 180.7, about one-fifth as many. Denver, the most volatile city in the set, records 281.6 — eight times San Diego's count. Los Angeles, the closest peer, runs 45.6, about 1.29 times San Diego's rate. Same coastal Southern California regime, with San Diego at the calm end of it.

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.

For people who track barometric pressure alongside their symptoms, San Diego is among the least eventful places in the country to do it. The city averages 35.4 days a year with a 24-hour change of at least 0.18 inHg (6 hPa) and just 5.3 days with a change of at least 0.30 inHg (10 hPa) — the latter ranks 49th of 50 cities and is roughly 1/16th the national median of 86.1. Significant 24-hour falls, the direction some pressure-sensitive people report noticing most, occur on about 15 days a year.

The practical value here is concentration rather than absence. Drop days cluster in December (3.1), January (3.0), March (2.6), and February (2.5), while June records none at all and July 0.1. If you are watching the barometer for conditions many pressure-sensitive people report as triggers, that watch is realistically a four-month one. From May through October, San Diego's pressure trace is close to flat, and the sharpest drop the city has recorded in ten years — 0.50 inHg (16.8 hPa) — is smaller than what Denver (-1.16 inHg / -39.2 hPa) and Tampa (-1.10 inHg / -37.2 hPa) have recorded.

Against other cities the contrast is stark. Denver logs 177.5 significant drop days a year, 11.8 times San Diego's 15, and its pressure standard deviation of 0.24 inHg (8.17 hPa) is more than double San Diego's 0.11 inHg (3.64 hPa). Los Angeles is the nearest comparison at 45.6 swing days and 7.5 big-swing days, slightly more active. Miami is the only city in the 50-city set that is calmer. One caveat worth keeping in mind: a low swing rank does not always mean a low ceiling — Tampa ranks 48th on swing days yet has recorded that 1.10 inHg (37.2 hPa) drop. San Diego's ceiling is genuinely low, which is what makes the August 2023 event stand out so sharply against everything around it.

Seasonal patterns

The active season is narrow and it is winter. January averages 7.0 significant swing days, December 6.5, February 6.3, and March 5.8 — together, December through March accounts for 25.6 of the year's 35.4 swing days, about 72% of the total. Monthly variability peaks in February at 3.88 hPa, and monthly mean pressure peaks in January at 30.08 inHg (1018.7 hPa), with December close behind at 30.06 inHg (1018.1 hPa). This is the only stretch of the year when Pacific storm tracks dip far enough south to reach 32.7°N with any regularity.

Summer is effectively a null zone. June averaged 0.0 significant swing days per year over the full decade, July 0.1, and August 0.4. July also has the lowest monthly variability of the year at 1.73 hPa. Mean pressure bottoms out in September at 29.89 inHg (1012.1 hPa), with June and August at 29.90 inHg (1012.7 and 1012.6 hPa). The subtropical high and the marine layer hold the barometer nearly motionless for months at a stretch.

The extremes reinforce the seasonal shape — with one exception. The record high of 30.45 inHg (1031.3 hPa) came on January 27, 2017. Four of the five sharpest 24-hour drops on record are winter events: -0.50 inHg (-16.8 hPa) ending February 17, 2017, the largest in the dataset; -0.40 inHg (-13.7 hPa) on January 20, 2017; another -0.40 inHg (-13.7 hPa) on December 16, 2017; and -0.39 inHg (-13.2 hPa) on February 21, 2019. The outlier is the record low of 29.39 inHg (995.2 hPa), set at 3 PM on August 20, 2023 — in the calmest month of the year — one hour after a -0.44 inHg (-14.8 hPa) 24-hour fall, the second-largest on record. That single August event is the exception that defines the rule.

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

• Los Angeles, CA
• Las Vegas, NV
• Phoenix, AZ
• Fresno, CA
• Tucson, AZ
• San Jose, CA

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