Indiana · 214 m elevation

Barometric Pressure in Indianapolis, IN

• 30.05Average pressure (inHg, sea level)
• 198.7Swing days a year · 19th of 50
• 109.3Big-swing days a year (≥10 hPa)
• 115.0Significant 24h drop days a year

Overview

Indianapolis averages 30.05 inHg (1017.7 hPa) and 198.7 significant pressure swing days a year — 26.1 in January but only 4.7 in August. Full data.

Indianapolis averages 30.05 inHg (1017.7 hPa) at sea-level equivalent, with a median of 30.04 inHg (1017.2 hPa). Most hours fall between 29.73 inHg (1006.6 hPa) and 30.42 inHg (1030.1 hPa) — the 5th and 95th percentiles of ten years of hourly data. The standard deviation is 0.21 inHg (7.11 hPa), just above the national median of 6.87 hPa.

The city sits at 214 meters, and that matters for anyone reading an uncorrected instrument. Mean station pressure is 29.29 inHg (992 hPa), about 0.76 inHg (25.7 hPa) below the sea-level figures quoted in forecasts. A home barometer that hasn't been calibrated to altitude will hover near 29.3 inHg on an ordinary day, not 30.05 — the readings aren't wrong, they're just uncorrected.

Nationally, Indianapolis ranks #19 of 50 for significant swing days, meaning 24-hour changes of at least 0.18 inHg (6 hPa), at 198.7 per year against a national median of 180.7. The more revealing numbers are the intensity ranks: #17 for big-swing days at 109.3 per year — 1.27 times the national median of 86.1 — and #11 for largest single 24-hour drop. Roughly 55% of Indianapolis swing days are big-swing days of 0.30 inHg (10 hPa) or more, against about 48% for the median city. This is not a place that fidgets. It sits quiet, then moves hard. The typical 24-hour change is only 0.10 inHg (3.5 hPa), but the 95th percentile is 0.42 inHg (14.3 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.

For people who track barometric pressure, the calendar in Indianapolis matters more than the annual average. The city logs 115 drop days per year — 24-hour falls of at least 0.18 inHg (6 hPa), the pattern many pressure-sensitive people report as a trigger. They cluster hard: 16.0 in February, 15.5 in March and 15.4 in January, against 2.1 in August and 2.8 in July. February carries more than seven times the drop-day load of August.

Against other cities, Indianapolis lands in the upper-middle tier with an intensity bias. It runs about 85% of Chicago's swing days (198.7 vs. 233.7) on the same storm track, and is nearly a statistical twin of Columbus, Ohio, at 204.2 swing days and 108.9 big-swing days — though Indianapolis edges it slightly on big swings. The sharper contrast is local: Louisville, roughly 110 miles south, records 91.8 big-swing days to Indianapolis's 109.3, so Indianapolis carries 1.19 times its neighbor's load of large moves. Against the calm end of the country, Indianapolis has ten times Miami's swing days and 34 times its big-swing days, and reaches about 64% of national leader Colorado Springs's 171.6 big-swing days.

The practical read: mid-November through March is when this city most often produces the conditions many pressure-sensitive people report as triggers — frequent deep lows, 24-hour changes reaching past 0.42 inHg (14.3 hPa) in the top 5% of days, and cold-season events like the -1.20 inHg (-40.7 hPa) collapse ending January 9, 2024. July through September is the reliably quiet stretch, with fewer than nine swing days a month and half of all 24-hour changes under 0.10 inHg (3.5 hPa). If you keep a symptom log, the seasonal signal in this city is unusually easy to see.

Seasonal patterns

Treat Indianapolis as two different pressure climates sharing one calendar. January produces 26.1 significant swing days and a monthly standard deviation of 0.28 inHg (9.41 hPa). August produces 4.7 swing days and a standard deviation of 0.10 inHg (3.46 hPa) — a 5.6-fold seasonal difference, and a lower month-to-month spread than Jacksonville's year-round standard deviation of 4.85 hPa. November through March each deliver at least 21.6 swing days; June through September each stay at or below 8.8.

The driver is the position of the winter storm track. From November through March, the jet stream and Ohio Valley cyclogenesis run directly over central Indiana, dragging deep lows across the region in sequence. By midsummer the jet has retreated north, leaving the area under weak, humid flow where convection — not synoptic systems — controls the weather, and the barometer barely registers it. Monthly means follow suit: 30.14 inHg (1020.7 hPa) in January and 30.13 inHg (1020.5 hPa) in November, versus a June low of 29.95 inHg (1014.2 hPa).

The extremes are almost entirely a cold-season phenomenon. The record high of 30.96 inHg (1048.3 hPa) came on February 9, 2019; the record low of 28.91 inHg (978.9 hPa) on March 3, 2023 — a lifetime span of 2.05 inHg (69.4 hPa). All five of the sharpest 24-hour drops on record fell between November and March, three of them in January: -1.20 inHg (-40.7 hPa) ending January 9, 2024; -0.99 inHg (-33.5 hPa) ending March 3, 2023 at the record low itself; -0.95 inHg (-32.3 hPa) on January 18, 2020; -0.85 inHg (-28.8 hPa) on January 9, 2015; and -0.85 inHg (-28.7 hPa) on November 18, 2017. The fastest six-hour fall was -0.59 inHg (-20.1 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

• Louisville, KY
• Chicago, IL
• Columbus, OH
• St. Louis, MO
• Detroit, MI
• Milwaukee, WI

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