Wisconsin · 189 m elevation

Barometric Pressure in Milwaukee, WI

• 30.03Average pressure (inHg, sea level)
• 242.7Swing days a year · 5th of 50
• 146.5Big-swing days a year (≥10 hPa)
• 140.7Significant 24h drop days a year

Overview

Milwaukee logs 242.7 significant pressure swing days a year — 5th highest of 50 US cities. Typical pressure 30.03 inHg (1016.8 hPa). Winter dominates.

Milwaukee's barometer averages 30.03 inHg (1016.8 hPa), with a median of 30.02 inHg (1016.6 hPa). Most hours over the 2015–2024 record fall between roughly 29.66 inHg (1004.3 hPa) and 30.42 inHg (1030 hPa) at the 5th and 95th percentiles. The standard deviation is 0.23 inHg (7.84 hPa), ninth widest among the 50 cities tracked here and above the national median of 6.87 hPa.

The number that defines Milwaukee is not spread but cadence. The city records 242.7 significant swing days per year — days when pressure moves at least 0.18 inHg (6 hPa) over 24 hours — ranking 5th of 50 against a national median of 180.7, or 1.34 times the typical US city. Big-swing days of 0.30 inHg (10 hPa) or more come 146.5 times a year, also 5th nationally and 1.70 times the median of 86.1. That works out to roughly two days in three crossing the significant threshold and about four days in ten clearing the big-swing bar. The median 24-hour change is 0.13 inHg (4.4 hPa); the 95th percentile is 0.48 inHg (16.3 hPa).

Milwaukee sits at 189 meters (620 feet), and that shows up on uncorrected instruments. Mean station pressure is 29.35 inHg (993.8 hPa) against the sea-level mean of 30.03 inHg (1016.8 hPa) — a standing gap of about 0.68 inHg (23 hPa). A home barometer that has not been set to altitude will read consistently low by that amount. The offset is fixed, so day-to-day trends remain accurate even if the absolute number does not match the airport report.

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, Milwaukee is one of the more demanding places in the country. Significant swings occur on 242.7 days a year and big swings on 146.5 — both 5th of 50 cities. Falling pressure, the pattern many pressure-sensitive people report as a trigger, accounts for 140.7 drop days annually. The distinguishing feature is repetition rather than severity: Milwaukee's single largest 24-hour drop ranks only 17th nationally, but its frequency of large moves is near the top of the list.

Seasonally, December through March is the demanding stretch — 25 to 28 swing days a month, with 15 to 16 of those being drops. July and August are the reprieve, with 9.3 and 9.4 swing days and only 4.4 to 4.7 drop days, alongside the year's calmest variability at 4.29 hPa in July. Late spring is the transition: May falls to 19.0 swing days, then June to 14.0.

In national context, Milwaukee sits in the western Great Lakes storm corridor alongside Minneapolis (249.9 swing days, 4th) and Chicago (233.7, 9th) — Milwaukee runs about nine more swing days and thirteen more big-swing days per year than Chicago, 90 miles down the lakeshore. It reaches roughly 86% of Denver's national-leading 281.6 swing days. Against the calm end of the scale the gap is enormous: 12.3 times Miami's 19.8 swing days and 5.3 times Los Angeles's 45.6, with 46 times Miami's big-swing count. Anyone arriving from a Sun Belt or Pacific coast city is encountering a fundamentally different pressure environment, and the difference is concentrated in the cold half of the year.

Seasonal patterns

The seasonal split here is unusually sharp. December leads with 27.5 significant swing days, followed by January at 27.0 and March at 26.3. July bottoms out at 9.3 and August at 9.4 — barely a third of the winter rate. Month-to-month variability follows the same curve: standard deviation peaks in February at 10.1 hPa and January at 9.94 hPa, then collapses to 4.29 hPa in July. Drop days, meaning significant 24-hour falls, run 16.3 in both January and December against 4.4 in July.

The driver is the winter position of the polar jet stream. From late fall through early spring, Alberta Clippers and Colorado lows track directly through the western Great Lakes, delivering one pressure couplet after another. In summer the jet retreats north into Canada, gradients slacken, and Milwaukee settles into long stretches of near-flat traces. Monthly mean pressure varies far less than the day-to-day churn: January averages 30.11 inHg (1019.5 hPa) and June 29.93 inHg (1013.4 hPa), a seasonal cycle of only about 0.18 inHg (6.1 hPa).

The extremes concentrate in the same window. All five of the sharpest 24-hour drops on record landed in January or February: -1.12 inHg (-37.8 hPa) ending January 18, 2020; -1.09 inHg (-37.0 hPa) on February 24, 2019; -1.09 inHg (-37.0 hPa) on January 9, 2024; -1.09 inHg (-36.9 hPa) on January 10, 2017; and -1.02 inHg (-34.7 hPa) on February 19, 2016. The largest 24-hour rise, +1.32 inHg (+44.6 hPa), exceeds the largest fall — the signature of arctic high pressure building in behind a departing storm. The record high of 30.97 inHg (1048.9 hPa) came on February 9, 2019; the record low of 29.05 inHg (983.8 hPa) on December 23, 2015. The full span is 1.92 inHg (65.1 hPa). Short-window moves can be steep too: the sharpest six-hour fall on record is -0.50 inHg (-16.9 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

• Chicago, IL
• Indianapolis, IN
• Detroit, MI
• Minneapolis, MN
• St. Louis, MO
• Columbus, OH

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