Culbertson, Montana · field elev 1,953 ft
Density Altitude at Big Sky Field (S85)
Big Sky Field sits at 1,953 ft, and even a typical July afternoon (87 °F) only lifts density altitude to about 4,151 ft — heat still trims performance, but the field rarely turns high-and-hot.
Typical density altitude by month
| Month | Avg temp °F | DA at avg temp | Afternoon high °F | DA on a typical afternoon |
|---|---|---|---|---|
| January | 13.3 | −706 ft | 24.4 | 88 ft |
| February | 18.3 | −345 ft | 29.8 | 467 ft |
| March | 31.0 | 550 ft | 43.5 | 1,404 ft |
| April | 44.7 | 1,484 ft | 59.4 | 2,452 ft |
| May | 55.5 | 2,199 ft | 70.7 | 3,174 ft |
| June | 64.6 | 2,787 ft | 79.0 | 3,692 ft |
| July | 71.1 | 3,199 ft | 86.5 | 4,151 ft |
| August | 70.0 | 3,130 ft | 86.5 | 4,151 ft |
| September | 59.6 | 2,465 ft | 75.7 | 3,487 ft |
| October | 45.0 | 1,504 ft | 58.9 | 2,420 ft |
| November | 29.0 | 411 ft | 40.5 | 1,201 ft |
| December | 17.2 | −424 ft | 27.9 | 334 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 S85
DENSITY ALTITUDE
Field elevation 1,953 ft — the air behaves like 4,182 ft.
- PRESSURE ALT
- 1,954 ft
- ISA DEVIATION
- —
- RULE-OF-THUMB DA
- —
- AIR DENSITY INDEX
- —
- AIR DENSITY
- —
- 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
- 5U6 — Fairview
Fairview · elev 2,152 ft
- PO1 — Poplar Municipal
Poplar · elev 2,037 ft
- KSDY — Sidney-Richland Regional
Sidney · elev 1,985 ft
- KPWD — Sher-Wood
Plentywood · elev 2,264 ft
- 7U8 — Richey
Richey · elev 2,494 ft
- KOLF — L M Clayton
Wolf Point · elev 1,989 ft
- 9S2 — Scobey
Scobey · elev 2,434 ft
- 4U6 — Circle Town County
Circle · elev 2,441 ft
Frequently asked questions
How high does density altitude get at S85 in summer?
On a typical July afternoon — around 87 °F at the nearest NOAA normals station — density altitude at Big Sky Field reaches roughly 4,151 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 S85 on an average day?
It swings with the seasons: from roughly −706 ft at the coldest month's average temperature to about 3,199 ft at the warmest month's — all from a constant field elevation of 1,953 ft. The month-by-month table above carries the full year.
What is the field elevation of Big Sky Field?
1,953 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is S85 (FAA), in Culbertson, Montana.