Fort Payne, Alabama · field elev 877 ft

Density Altitude at Isbell Field (4A9)

Isbell Field sits at 877 ft, and even a typical July afternoon (91 °F) only lifts density altitude to about 3,104 ft — heat still trims performance, but the field rarely turns high-and-hot.

worst typical month: July · ≈3,104 ft station: FT PAYNE · 2 mi away normals vintage 1991–2020

Typical density altitude by month

From NOAA 1991–2020 monthly normals at FT PAYNE (2 mi from the field) · standard pressure, dry air
Month Avg temp °F DA at avg temp Afternoon high °F DA on a typical afternoon
January 41.8 −47 ft 52.2 652 ft
February 46.2 251 ft 56.7 950 ft
March 53.7 752 ft 65.1 1,496 ft
April 61.5 1,263 ft 73.5 2,032 ft
May 69.7 1,791 ft 81.0 2,502 ft
June 77.1 2,259 ft 87.7 2,915 ft
July 80.4 2,465 ft 90.8 3,104 ft
August 79.7 2,421 ft 90.2 3,067 ft
September 74.7 2,108 ft 85.8 2,798 ft
October 63.9 1,419 ft 76.1 2,196 ft
November 52.6 679 ft 64.1 1,432 ft
December 45.1 177 ft 55.4 864 ft

▲ above 5,000 ft · ⚠ above 8,000 ft. These are planning references at standard pressure and dry air — afternoon humidity and low pressure both push the real number higher. Run today's values below.

Run today’s numbers for 4A9

Altimeter-style gauge: field elevation and density altitude needles 03691215 DENSITY ALT ×1,000 FT 3,116 DENSITY ALTITUDE · FEET
field elevation density altitude

DENSITY ALTITUDE 3,116 ft

Field elevation 877 ft — the air behaves like 3,116 ft.

PRESSURE ALT
878 ft
ISA DEVIATION
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RULE-OF-THUMB DA
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AIR DENSITY INDEX
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AIR DENSITY
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WATER · GRAINS/LB
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For training and reference · verify with official sources and your POH before flight · no tool on this site renders a go / no-go judgment

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Frequently asked questions

How high does density altitude get at 4A9 in summer?

On a typical July afternoon — around 91 °F at the nearest NOAA normals station — density altitude at Isbell Field reaches roughly 3,104 ft at standard pressure. Hotter-than-normal days, low pressure, and humidity all push it higher, so run the day's actual numbers before flying.

What is the density altitude at 4A9 on an average day?

It swings with the seasons: from roughly −47 ft at the coldest month's average temperature to about 2,465 ft at the warmest month's — all from a constant field elevation of 877 ft. The month-by-month table above carries the full year.

What is the field elevation of Isbell Field?

877 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is 4A9 (FAA), in Fort Payne, Alabama.