Florida · 6 m elevation

Barometric Pressure in Jacksonville, FL

• 30.06Average pressure (inHg, sea level)
• 81.7Swing days a year · 40th of 50
• 22.1Big-swing days a year (≥10 hPa)
• 40.3Significant 24h drop days a year

Overview

Jacksonville averages 30.06 inHg (1017.9 hPa) with just 81.7 pressure swing days a year — #40 of 50 cities — but its worst 24h drop hit 0.84 inHg.

Jacksonville's barometer sits at a mean of 30.06 inHg (1017.9 hPa), with a median reading of 30.06 inHg (1017.8 hPa) and a standard deviation of just 0.14 inHg (4.85 hPa). Ninety percent of hours over the 2015–2024 record fall between 29.84 and 30.30 inHg (1010.4 and 1026.2 hPa). That places Jacksonville #43 of 50 for variability, essentially tied with San Francisco.

The day-to-day numbers are quieter still. The typical 24-hour change here is 0.06 inHg (1.9 hPa) — a needle that barely moves. The middle 90 percent of daily changes run from a 0.17 inHg (5.6 hPa) fall to a 0.19 inHg (6.3 hPa) rise. Significant swing days, meaning a 24-hour change of 0.18 inHg (6 hPa) or more, come 81.7 times a year, ranking #40 of 50. Big-swing days of 0.30 inHg (10 hPa) or more come 22.1 times, ranking #41. The national medians are 180.7 and 86.1 — Jacksonville sees less than half the swing days and roughly a quarter of the big ones.

At 6 meters of elevation, station pressure and sea-level pressure are effectively the same number here: the surface mean is 30.04 inHg (1017.2 hPa) against an MSL mean of 30.06 inHg (1017.9 hPa), a 0.02 inHg (0.7 hPa) offset. An uncorrected home barometer in Jacksonville reads within a hundredth of an inch of published values, which is not true in most of the country.

The one place Jacksonville breaks its own pattern is at the extreme. Its deepest 24-hour fall, 0.84 inHg (28.6 hPa), ranks #28 of 50 — a dozen places above where its everyday volatility sits. That gap is the city's real signature: long flat stretches, punctuated by a handful of very steep falls.

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 pressure, Jacksonville is a low-frequency city with a concentrated season. Drop days — significant 24-hour falls of 0.18 inHg (6 hPa) or more — average 40.3 a year, and they cluster hard: 8.2 in January, 7.1 in February, 5.8 in March, 5.5 in December. From May through September the total is about 3.2 drop days across five months, with July averaging zero. The conditions many pressure-sensitive people report as triggers show up here mostly between December and March, then largely disappear for the summer.

Compared nationally, that is a light load. Denver, the most volatile city in this set, records 281.6 swing days a year — 3.4 times Jacksonville's 81.7 — and 169.8 big-swing days against Jacksonville's 22.1, a factor of 7.7. Against the national medians, Jacksonville sees less than half the swing days and about a quarter of the big ones. Its closest peers by annual count are New Orleans at 80.8 and San Francisco at 80.6, though the mechanisms behind those numbers differ entirely.

Jacksonville is not the flattest place in Florida, and the distinction matters. Miami logs 19.8 swing days a year; Jacksonville has 4.1 times as many, and 6.9 times the big-swing days (22.1 against 3.2). Tampa logs 42.8; Jacksonville has 1.9 times as many swing days and 2.4 times the big ones. Jacksonville is the most variable of the three by a clear margin. The other feature worth knowing about is the tail: tropical season delivers few events, but large ones — the September 11, 2017 fall of 0.84 inHg (28.6 hPa) in 24 hours is nearly three times the 0.30 inHg (10 hPa) big-swing threshold.

Seasonal patterns

The calendar splits cleanly in two. December through March carries the bulk of the year's activity: January averages 15.7 swing days, February 14.0, December 12.1, March 10.9. Monthly variability peaks in January at 0.17 inHg (5.92 hPa). These are frontal passages reaching the northern Florida coast — the same cold fronts that sweep the Southeast, arriving with enough gradient behind them to move a barometer.

May through September is close to inert, with 7.5 swing days across the five months combined. June averages 1.1, August 0.5, and July has produced zero across the full ten-year record. July's monthly standard deviation is 0.08 inHg (2.76 hPa). The Bermuda high dominates, gradients collapse, and summer weather here is convective rather than synoptic — afternoon storms that dump rain without a meaningful pressure signature. Monthly mean pressure follows the same shape, running highest in January and December at 30.14 inHg (1020.7 and 1020.6 hPa) and bottoming in September at 29.98 inHg (1015.2 hPa), the heart of tropical season.

The extremes come from both regimes. The record high, 30.67 inHg (1038.6 hPa), was set on January 9, 2017. The record low, 29.09 inHg (985.1 hPa), came on the morning of September 11, 2017 — the same hour that closed out the sharpest 24-hour drop in the record, 0.84 inHg (28.6 hPa), from a tropical system. The rest of the top five splits between seasons: 0.78 inHg (26.5 hPa) ending December 17, 2023; 0.71 inHg (23.9 hPa) on October 7, 2016; 0.67 inHg (22.6 hPa) on January 9, 2024; and 0.55 inHg (18.5 hPa) on November 10, 2022. The fastest six-hour fall on record is 0.46 inHg (15.5 hPa), and the largest 24-hour rise is 0.78 inHg (26.5 hPa).

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

• Tampa, FL
• Atlanta, GA
• Miami, FL
• Charlotte, NC
• Raleigh, NC
• Nashville, TN

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