Maryland · 29 m elevation

Barometric Pressure in Baltimore, MD

• 30.05Average pressure (inHg, sea level)
• 222.3Swing days a year · 13th of 50
• 117.9Big-swing days a year (≥10 hPa)
• 125.4Significant 24h drop days a year

Overview

Baltimore averages 222.3 significant pressure swing days a year, ranking #13 of 50 US cities. Ten-year data on records, seasonal patterns, and extremes.

Baltimore's mean sea-level pressure from 2015 through 2024 was 30.05 inHg (1017.6 hPa), measured across 87,672 hours. Half of all readings cluster near the 30.04 inHg (1017.4 hPa) median, but the outer edges are wide: the 5th percentile sits at 29.70 inHg (1005.8 hPa) and the 95th at 30.42 inHg (1030.2 hPa). The standard deviation is 0.22 inHg (7.43 hPa), 14th highest of the 50 cities tracked.

At 29 meters elevation, Baltimore has almost no altitude correction to worry about. Station pressure averages 29.95 inHg (1014.1 hPa) against the sea-level-adjusted 30.05 inHg — a gap of just 0.10 inHg. An uncorrected home barometer here reads close to what forecasts quote. In a high-elevation city like Denver, at 1,615 meters, the same instrument would read far lower than the sea-level figure.

Nationally, Baltimore ranks #13 of 50 for significant swing days (222.3 per year, against a national median of 180.7) and #14 for big-swing days (117.9 versus a median of 86.1). That places it in the volatile upper third without being extreme. The exception is the tail. Baltimore's largest 24-hour fall on record is 1.31 inHg (44.3 hPa), which ranks #6 of 50 — behind only Boston, New York, Detroit, Philadelphia, and Cleveland, and within striking distance of Boston's national-leading 1.52 inHg (51.5 hPa). Routine days here are moderately restless; the worst days are near the top of the list.

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.

The useful thing about Baltimore for anyone who tracks barometric pressure is that its volatility is seasonal rather than constant. The city logs 222.3 significant swing days per year (a 24-hour change of 0.18 inHg / 6 hPa or more) and 117.9 big-swing days (0.30 inHg / 10 hPa or more), of which 125.4 are drops rather than rises. The median day moves only 0.12 inHg (4 hPa), but one day in twenty moves at least 0.45 inHg (15.1 hPa) — the kind of rapid change many pressure-sensitive people report as a trigger.

November through March carries the load, with January and February each above 26 swing days and February holding the year's heaviest drop count at 16.2. July and August are the quiet end of the range: 6.7 and 7.0 swing days, 3.5 and 3.8 drop days. Falling pressure — the pattern most often described as a trigger — is concentrated the same way, with more than four times as many drop days in February as in July.

Comparatively, Baltimore records 11.2 times the swing days of Miami (222.3 versus 19.8) and 36.8 times the big-swing days (117.9 versus 3.2). It reaches 79% of Denver's national-leading 281.6 swing days but only 69% of Denver's 169.8 big-swing days. Along I-95 the three neighboring cities form one pressure climate: Philadelphia at 231.7 swing days (#10), Baltimore at 222.3 (#13), Washington at 218.6 (#15). Where Baltimore separates from cities ranked near it is at the extreme end — five separate 24-hour falls above 1.00 inHg in ten years, every one of them between mid-December and mid-March.

Seasonal patterns

The calendar is lopsided. January produces 26.8 significant swing days, February 26.5, and December 24.9. July produces 6.7 — four times fewer than January. Monthly variability follows the same curve, from 0.27 inHg (9.25 hPa) in January down to 0.12 inHg (4.03 hPa) in July. Drop days peak in February at 16.2 and bottom out in July at 3.5. Roughly 127 of the year's 222 swing days fall in the November-through-March window.

The driver is the cold-season storm track. From late fall through early spring the polar jet sits over or near the Mid-Atlantic, steering lows up the coast and letting cold high pressure build in behind them. Monthly means peak in November and December at 30.13 inHg (1020.3 and 1020.2 hPa), and bottom in June at 29.95 inHg (1014.3 hPa). In midsummer Baltimore sits under the western flank of the Bermuda high, where gradients are weak and the barometer has little to do.

The record high, 30.96 inHg (1048.3 hPa), came on December 14, 2024. The record low, 28.98 inHg (981.4 hPa), came on February 7, 2020. Between them lies a ten-year range of 1.98 inHg (66.9 hPa). All five of the steepest 24-hour drops on record are cold-season events: 1.31 inHg (44.3 hPa) ending January 10, 2024; 1.29 inHg (43.6 hPa) ending January 17, 2022; 1.13 inHg (38.3 hPa) ending December 18, 2023; 1.09 inHg (36.9 hPa) ending December 23, 2022; and 1.02 inHg (34.5 hPa) ending March 14, 2017. The fastest six-hour fall was 0.68 inHg (23.1 hPa). The largest 24-hour rise, 1.26 inHg (42.5 hPa), is nearly the mirror image of the largest fall — the same coastal-storm cycle running the other direction as high pressure fills in behind a departing low.

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

• Washington, DC
• Philadelphia, PA
• New York, NY
• Virginia Beach, VA
• Raleigh, NC
• Cleveland, OH

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