Massachusetts · 19 m elevation

Barometric Pressure in Boston, MA

• 30.01Average pressure (inHg, sea level)
• 257.6Swing days a year · 3rd of 50
• 158.7Big-swing days a year (≥10 hPa)
• 151.0Significant 24h drop days a year

Overview

Boston averages 30.01 inHg (1016.3 hPa) and recorded the largest 24-hour pressure drop of 50 US cities: 1.52 inHg (51.5 hPa) on March 14, 2017.

Boston sits 19 meters above sea level with a 2015-2024 mean sea-level pressure of 30.01 inHg (1016.3 hPa). Ninety percent of hours fall between 29.60 and 30.42 inHg (1002.3 and 1030.1 hPa), and the median reading, 30.01 inHg (1016.2 hPa), sits almost exactly on the mean. Because the city is essentially at sea level, station pressure averages 29.94 inHg (1013.9 hPa) — about 0.07 inHg (2.4 hPa) below the sea-level values quoted in forecasts. A home barometer set to raw station pressure will read slightly low, but the gap is small enough that Boston residents can take published numbers at face value.

What sets Boston apart is not its average but the violence of its individual events. Its sharpest 24-hour fall on record, 1.52 inHg (51.5 hPa), is the largest of any of the 50 cities in this dataset — larger than Denver's worst day at 1.16 inHg (39.2 hPa) and larger than New York's at 1.41 inHg (47.6 hPa). Boston also ranks #3 of 50 for significant swing days, #3 for big-swing days, and #2 for overall pressure variability, with a standard deviation of 0.25 inHg (8.44 hPa) against a national median of 6.87 hPa.

Boston is the only near-sea-level city in the top tier of volatility. Denver, Colorado Springs, and Salt Lake City reach comparable ranks through altitude and terrain; Boston gets there through the winter storm track. Coastal lows deepening over the relatively warm shelf water of the Gulf of Maine, along a sharp temperature contrast between the continent and the ocean, produce pressure falls that mountain cities rarely match. On a typical day the 24-hour change is 0.14 inHg (4.9 hPa); on a top-5% day it reaches 0.54 inHg (18.2 hPa).

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.

Boston averages 257.6 significant swing days per year — days with a 24-hour change of at least 0.18 inHg (6 hPa) — which is 1.43 times the national median of 180.7. Big-swing days, at least 0.30 inHg (10 hPa) in 24 hours, average 158.7 per year, 1.84 times the median of 86.1. Of those, 151 days per year are drops rather than rises. These are the conditions many pressure-sensitive people report as triggers, and Boston delivers them more often than all but two of the 50 cities studied.

The seasonal split is the practical detail. Drop days peak in February and March at 17.1 each, with January at 16.5 and December at 16.4. July is the quietest at 6.7 and August at 7.3 — roughly 2.5 times fewer falling-pressure days than late winter. For anyone tracking symptoms against a barometer, the December-through-March window is where Boston's activity concentrates, and midsummer offers a genuine stretch of stability.

For comparison, Boston records 13.0 times as many swing days as Miami (19.8) and 49.6 times as many big-swing days (3.2). Against Los Angeles, Boston's 95th-percentile 24-hour change of 0.54 inHg (18.2 hPa) is 3.1 times larger than LA's 0.17 inHg (5.9 hPa). Compared with New York on the same coast, Boston sees only about 7% more swing days but 1.16 times as many big-swing days — the difference is intensity rather than frequency. Denver logs more swing days overall (281.6), but Boston's largest single-day fall exceeds Denver's by 31%. Moving to Boston from the Southwest, the Gulf Coast, or California means a substantial change in how often and how fast pressure moves through the winter half of the year.

Seasonal patterns

Boston effectively runs two pressure climates a year. January is the most turbulent month, with a standard deviation of 0.31 inHg (10.33 hPa), followed closely by December at 0.30 inHg (10.14 hPa), February at 0.30 inHg (10.07 hPa), and March at 0.29 inHg (9.81 hPa). July is the calmest at 0.14 inHg (4.66 hPa) — less than half of January's variability — with August close behind at 0.15 inHg (4.95 hPa). In midsummer, Boston's numbers resemble a mid-pack city rather than a top-three one.

Significant swing days follow the same shape. March averages 27.5 per year and December 27.4, with January at 27.1 and November at 26.2. July bottoms out at 13.0 and August at 13.1. Monthly mean pressure varies far less than monthly variability does: June is the lowest month at 29.93 inHg (1013.4 hPa), and September and December tie for highest at 30.07 inHg (1018.2 hPa).

The extremes are all cold-season events. The record high of 30.94 inHg (1047.7 hPa) came on December 14, 2024; the record low of 28.66 inHg (970.7 hPa) on February 7, 2020 — a 2.27 inHg (77.0 hPa) span across ten years. Every one of the five sharpest 24-hour drops occurred between December and March: -1.52 inHg (51.5 hPa) ending March 14, 2017; -1.49 inHg (50.4 hPa) ending January 10, 2024; -1.41 inHg (47.6 hPa) ending December 23, 2022; and -1.35 inHg (45.6 hPa) on both January 4, 2018 and January 17, 2022. The fastest six-hour fall on record was 0.83 inHg (28.0 hPa), and the largest 24-hour rise was 1.45 inHg (49.1 hPa), showing that recovery behind these systems can be nearly as abrupt as the collapse ahead of them.

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

• New York, NY
• Philadelphia, PA
• Baltimore, MD
• Washington, DC
• Virginia Beach, VA
• Cleveland, OH

All 50 cities · Check any US location · Methodology