Arizona · 333 m elevation

Barometric Pressure in Phoenix, AZ

• 29.89Average pressure (inHg, sea level)
• 75.8Swing days a year · 44th of 50
• 17.7Big-swing days a year (≥10 hPa)
• 34.8Significant 24h drop days a year

Overview

Phoenix averages 75.8 significant pressure swing days a year (#44 of 50 US cities), with just 0.7 in July. Seasonal patterns, records, and swing data.

Phoenix runs at a mean sea-level pressure of 29.89 inHg (1012.3 hPa) — the lowest average of the 50 US cities in this dataset. That is the signature of a desert thermal low: heated air over the Sonoran Desert keeps the column lighter than anywhere on the coasts or in the Midwest. About 90% of hours fall between 29.67 inHg (1004.7 hPa) and 30.17 inHg (1021.7 hPa), and the standard deviation of 0.15 inHg (5.23 hPa) ranks #41 of 50 for variability.

Elevation matters here more than most people expect. Phoenix sits at 333 m (1,093 ft), and the average station pressure — what a barometer actually measures before any correction — is 28.77 inHg (974.4 hPa), about 1.12 inHg (37.9 hPa) below the sea-level-adjusted figure quoted in forecasts. A home barometer reading near 28.8 inHg in Phoenix is not broken; it simply hasn't been set to sea-level equivalent. Aneroid units usually have an adjustment screw for exactly this.

Nationally, Phoenix is quiet. It logs 75.8 significant swing days per year (24-hour change of 6 hPa or more), ranking #44 of 50 against a national median of 180.7 — roughly 2.4 times fewer. Big-swing days of 10 hPa or more come 17.7 times a year, #44 of 50, against a median of 86.1. Denver, the most volatile city in the set, records 3.7 times as many swing days and 9.6 times as many big-swing days. The more telling number is the ceiling: Phoenix's deepest 24-hour fall in ten years was 0.44 inHg (14.9 hPa), the mildest worst-case drop of all 50 cities — gentler than Miami's or San Diego's. Phoenix is not just calm on average; its extremes are capped.

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 alongside their symptoms, Phoenix registers as one of the quietest large US cities on this measure — and the useful information is about timing, not intensity. A typical 24-hour change here is 0.06 inHg (1.9 hPa), and only 5% of days exceed 0.22 inHg (7.3 hPa). Significant drops — 24-hour falls of 6 hPa or more, the direction most often reported as a trigger — occur 34.8 times a year, or roughly one day in ten.

The calendar is unusually clean. February is the peak month with 7.0 drop days, followed by December at 6.1 and January at 5.6; March adds 4.6. June is essentially blank at 0.1 drop days, with July at 0.2 and August at 0.5. If you are pressure-sensitive in Phoenix, the window that matters runs roughly December through March, and the five-month stretch from May into September produces conditions many pressure-sensitive people report as triggers on only a handful of days total. The monsoon may bring dust, humidity, and thunderstorms, but it does not bring the sustained 24-hour pressure declines this dataset measures.

Comparatively, Phoenix sees about 42% of the national median swing-day count and roughly a fifth of the median big-swing days. Denver residents encounter 9.6 times as many big-swing days; Boston's deepest recorded 24-hour fall is 3.5 times Phoenix's. Even Las Vegas, the nearest large desert peer, logs 1.7 times as many swing days, sitting closer to the Pacific storm track. Only Fresno, Tucson, Los Angeles, Tampa, San Diego, and Miami rank calmer. Phoenix is not the flattest barometer in the country — it records 3.8 times Miami's swing days — but its combination of infrequent swings and an unusually low extreme ceiling makes it distinctive among large US cities.

Seasonal patterns

Phoenix effectively has two barometric climates. From December through March, Pacific storm systems and cutoff lows reach Arizona and the barometer moves: February leads with 12.8 swing days, followed by December at 12.3, January at 11.8, and March at 10.0. December, January, and February alone account for 36.9 swing days — about half the annual total. Monthly variability peaks in February at 0.14 inHg (4.91 hPa).

From May through September the barometer nearly flatlines. July averages 0.7 swing days, August 0.8, June 0.9 — that trio contributes about 3% of the year's total. There is a paradox worth naming: this is monsoon season, the most dramatic weather Phoenix gets. But monsoon thunderstorms are convective and local. They spike pressure over minutes to an hour, not across the 24-hour window this metric counts. Monthly means fall from 30.07 inHg (1018.3 hPa) in January to 29.75 inHg (1007.4 hPa) in June — a slow 0.32 inHg (10.9 hPa) seasonal decline as the summer heat low deepens, larger than most individual storms produce.

The ten-year record high of 30.53 inHg (1033.9 hPa) came on January 28, 2017. The record low of 29.43 inHg (996.7 hPa) came on October 11, 2023 — in 87,672 hours of data, pressure never went lower. Total range across the decade: 1.10 inHg (37.2 hPa). The five sharpest 24-hour falls are tightly clustered near the same value, which is why the ceiling looks like a real limit: -0.44 inHg (-14.9 hPa) ending March 30, 2017; -0.44 inHg (-14.8 hPa) on January 23, 2023; -0.43 inHg (-14.7 hPa) on December 16, 2017; -0.43 inHg (-14.5 hPa) on January 7, 2024; and -0.42 inHg (-14.2 hPa) on December 24, 2016. Four of the five landed in December or January. Rises outrun falls here — the largest 24-hour gain was 0.68 inHg (23.1 hPa), well beyond anything on the drop side, reflecting cold air surging in behind a front.

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

• Tucson, AZ
• Las Vegas, NV
• San Diego, CA
• Albuquerque, NM
• El Paso, TX
• Los Angeles, CA

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