Fort Benton, Montana · field elev 2,869 ft
Density Altitude at Fort Benton (79S)
From a field elevation of 2,869 ft, a typical July afternoon at Fort Benton (86 °F) raises density altitude to about 5,258 ft — solidly into the range where performance charts deserve a close read.
Typical density altitude by month
| Month | Avg temp °F | DA at avg temp | Afternoon high °F | DA on a typical afternoon |
|---|---|---|---|---|
| January | 22.3 | 1,086 ft | 34.6 | 1,938 ft |
| February | 25.3 | 1,297 ft | 38.1 | 2,176 ft |
| March | 34.3 | 1,918 ft | 48.2 | 2,850 ft |
| April | 44.6 | 2,612 ft | 58.6 | 3,527 ft |
| May | 54.4 | 3,256 ft | 68.3 | 4,144 ft |
| June | 62.5 | 3,777 ft | 76.3 | 4,642 ft |
| July | 70.3 | 4,270 ft | 86.4 | 5,258 ft ▲ |
| August | 68.8 | 4,176 ft | 85.5 | 5,204 ft ▲ |
| September | 58.3 | 3,508 ft | 74.2 | 4,513 ft |
| October | 45.2 | 2,652 ft | 59.9 | 3,611 ft |
| November | 33.7 | 1,877 ft | 46.5 | 2,738 ft |
| December | 24.9 | 1,269 ft | 36.7 | 2,081 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 79S
DENSITY ALTITUDE caution
Field elevation 2,869 ft — the air behaves like 5,234 ft.
- PRESSURE ALT
- 2,871 ft
- ISA DEVIATION
- —
- RULE-OF-THUMB DA
- —
- AIR DENSITY INDEX
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- AIR DENSITY
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- WATER · GRAINS/LB
- —
For training and reference · verify with official sources and your POH before flight · no tool on this site renders a go / no-go judgment
Nearby Montana fields
- 5U8 — Geraldine
Geraldine · elev 3,185 ft
- 3U8 — Big Sandy
Big Sandy · elev 2,699 ft
- B70 — Tiber Dam
Tiber Dam · elev 3,023 ft
- KGTF — Great Falls International
Great Falls · elev 3,680 ft
- 5U0 — Denton
Denton · elev 3,594 ft
- KLTY — Liberty County
Chester · elev 3,185 ft
- 5U1 — Dutton
Dutton · elev 3,699 ft
- S64 — Stanford/Biggerstaff Field
Stanford · elev 4,328 ft
Frequently asked questions
How high does density altitude get at 79S in summer?
On a typical July afternoon — around 86 °F at the nearest NOAA normals station — density altitude at Fort Benton reaches roughly 5,258 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 79S on an average day?
It swings with the seasons: from roughly 1,086 ft at the coldest month's average temperature to about 4,270 ft at the warmest month's — all from a constant field elevation of 2,869 ft. The month-by-month table above carries the full year.
What is the field elevation of Fort Benton?
2,869 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is 79S (FAA), in Fort Benton, Montana.