Fairfield, Idaho · field elev 5,058 ft
Density Altitude at Fairfield/Frostenson Airfield (U86)
From a field elevation of 5,058 ft, a typical July afternoon at Fairfield/Frostenson Airfield (84 °F) raises density altitude to about 7,770 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 | 18.3 | 3,542 ft | 27.3 | 4,162 ft |
| February | 21.5 | 3,764 ft | 31.3 | 4,433 ft |
| March | 30.7 | 4,393 ft | 40.7 | 5,060 ft ▲ |
| April | 42.0 | 5,145 ft | 53.8 | 5,909 ft ▲ |
| May | 51.3 | 5,749 ft | 64.5 | 6,584 ft ▲ |
| June | 58.2 | 6,189 ft | 73.0 | 7,107 ft ▲ |
| July | 67.0 | 6,739 ft | 84.0 | 7,770 ft ▲ |
| August | 65.5 | 6,646 ft | 82.8 | 7,698 ft ▲ |
| September | 56.7 | 6,094 ft | 73.8 | 7,156 ft ▲ |
| October | 44.5 | 5,309 ft | 59.0 | 6,239 ft ▲ |
| November | 31.0 | 4,413 ft | 41.7 | 5,126 ft ▲ |
| December | 19.0 | 3,590 ft | 28.0 | 4,210 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 U86
DENSITY ALTITUDE caution
Field elevation 5,058 ft — the air behaves like 7,770 ft.
- PRESSURE ALT
- 5,060 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 Idaho fields
- U93 — Magic Reservoir
Hailey · elev 4,844 ft
- 1U9 — Pine
Pine · elev 4,232 ft
- KSUN — Friedman Meml
Hailey · elev 5,320 ft
- KGNG — Gooding Municipal
Gooding · elev 3,732 ft
- 55H — Atlanta
Atlanta · elev 5,500 ft
- U89 — Glenns Ferry Municipal
Glenns Ferry · elev 2,536 ft
- 2U0 — Smith Prairie
Prairie · elev 4,958 ft
- U87 — Smiley Creek
Smiley Creek · elev 7,206 ft
Frequently asked questions
How high does density altitude get at U86 in summer?
On a typical July afternoon — around 84 °F at the nearest NOAA normals station — density altitude at Fairfield/Frostenson Airfield reaches roughly 7,770 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 U86 on an average day?
It swings with the seasons: from roughly 3,542 ft at the coldest month's average temperature to about 6,739 ft at the warmest month's — all from a constant field elevation of 5,058 ft. The month-by-month table above carries the full year.
What is the field elevation of Fairfield/Frostenson Airfield?
5,058 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is U86 (FAA), in Fairfield, Idaho.