District of Columbia · 12 m elevation

Barometric Pressure in Washington, DC

• 30.05Average pressure (inHg, sea level)
• 218.6Swing days a year · 15th of 50
• 114.1Big-swing days a year (≥10 hPa)
• 123.3Significant 24h drop days a year

Overview

Washington, DC averages 30.05 inHg (1017.7 hPa) and 218.6 significant pressure swing days a year — but January runs 4.3x more turbulent than July.

Washington's mean sea-level pressure over the 2015–2024 record is 30.05 inHg (1017.7 hPa), with a median of 30.04 inHg (1017.4 hPa). Ninety percent of hours fall between 29.71 inHg (1006 hPa) and 30.42 inHg (1030.2 hPa), and the standard deviation is 0.22 inHg (7.34 hPa). On a typical day the 24-hour change is only 0.12 inHg (3.9 hPa) — small enough to go unnoticed. The tails are what matter here.

The city sits at 12 meters of elevation, so there is almost no altitude correction to think about. Mean station pressure is 30.01 inHg (1016.2 hPa) against a sea-level mean of 30.05 inHg (1017.7 hPa), a difference of about 0.04 inHg (1.5 hPa). A home barometer reading raw station pressure will run a hair below the values quoted in forecasts; anything calibrated to sea level should track the numbers on this page closely.

Nationally, Washington ranks #15 of 50 for significant swing days (218.6 per year, against a national median of 180.7) and #16 for big-swing days (114.1 per year against a national median of 86.1). That places it comfortably above average but well short of Denver at #1 with 281.6 swing days. The annual figure, though, is misleading — it averages a winter that behaves like a top-ten volatility city with a summer that behaves like the Gulf Coast. One number does stand out on its own: Washington's sharpest 24-hour fall, -1.29 inHg (-43.7 hPa), ranks #7 of 50 nationally, deeper than anything Denver recorded in the same decade.

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.

Washington averages 218.6 days a year with a 24-hour pressure change of at least 0.18 inHg (6 hPa), and 114.1 days with a change of at least 0.30 inHg (10 hPa) — conditions many pressure-sensitive people report as triggers. Of the significant-change days, 123.3 are drop days, meaning a fall rather than a rise. The 95th-percentile 24-hour move is 0.44 inHg (14.8 hPa), so roughly one day in twenty brings a change of that size or larger.

The calendar matters more than the annual total. December through March carry 24.5 to 27.0 swing days per month and 13.9 to 16.1 drop days. July and August carry 6.3 and 6.8 swing days and just 3.4 and 3.8 drop days. March is the peak month for falling pressure specifically, and September is the calmest month outside high summer at 11.4 swing days. For anyone logging symptoms against a barometer, the activity in this record is concentrated in the cold half of the year.

For comparison, Washington has about 11 times Miami's annual swing days (19.8) and nearly 36 times its big-swing days (3.2), and 1.89 times Atlanta's swing days (115.6) despite the two cities sharing a broad region. It is statistically almost identical to Baltimore, 40 miles north, which logs 222.3 swing days. Against the volatile end of the list, Washington sits at 78% of Denver's 281.6 and just behind Philadelphia's 231.7. The summary: a middling annual profile built from a genuinely turbulent winter and an unusually quiet summer.

Seasonal patterns

The seasonal split is the defining feature of Washington's pressure climate. January averages 27.0 significant swing days, February 26.2, and March 25.4. July averages 6.3 and August 6.8 — January runs about 4.3 times July's pace. Monthly variability follows the same curve: the standard deviation is 0.27 inHg (9.17 hPa) in January and 0.12 inHg (3.96 hPa) in July, less than half. Winter belongs to the storm track and to coastal cyclogenesis off the Delmarva; summer belongs to the Bermuda High, which flattens the gradient for weeks at a time. Monthly mean pressure is highest in November at 30.14 inHg (1020.5 hPa) and lowest in June at 29.96 inHg (1014.4 hPa).

One wrinkle: drop days — significant 24-hour falls — peak in March at 16.1, edging out February's 15.8 and January's 15.4, even though January has the most swing days overall. Late-winter and early-spring cyclones deepening off the mid-Atlantic coast produce the fastest sustained falls of the year, and March catches more of them than the depth of winter does.

The extremes cluster in the cold season without exception. The record high, 30.94 inHg (1047.9 hPa), came on December 14, 2024; the record low, 29.00 inHg (982.2 hPa), on February 7, 2020 — a total span of 1.94 inHg (65.7 hPa) across the decade. All five of the sharpest 24-hour drops fell between December and March: -1.29 inHg (-43.7 hPa) ending January 10, 2024; -1.27 inHg (-43.0 hPa) on January 17, 2022; -1.09 inHg (-36.8 hPa) on December 18, 2023; -1.07 inHg (-36.1 hPa) on December 23, 2022; and -0.94 inHg (-31.9 hPa) on March 14, 2017. The fastest six-hour fall on record was -0.68 inHg (-22.9 hPa), and the largest 24-hour rise was 1.22 inHg (41.4 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

• Baltimore, MD
• Philadelphia, PA
• Virginia Beach, VA
• New York, NY
• Raleigh, NC
• Cleveland, OH

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