Ketchum, Idaho · field elev 6,900 ft
Density Altitude at Twin Bridges (U61)
Twin Bridges is a genuine high-and-hot field: from 6,900 ft of elevation, a typical July afternoon (82 °F) pushes density altitude to about 9,898 ft — the airplane performs like it is 2,998 ft above the field before the wheels roll.
Typical density altitude by month
| Month | Avg temp °F | DA at avg temp | Afternoon high °F | DA on a typical afternoon |
|---|---|---|---|---|
| January | 19.0 | 5,886 ft | 30.5 | 6,662 ft ▲ |
| February | 22.4 | 6,118 ft | 33.7 | 6,874 ft ▲ |
| March | 32.3 | 6,781 ft | 43.6 | 7,519 ft ▲ |
| April | 40.3 | 7,305 ft | 52.9 | 8,111 ft ⚠ |
| May | 48.7 | 7,845 ft | 62.6 | 8,714 ft ⚠ |
| June | 56.5 | 8,336 ft | 71.8 | 9,274 ft ⚠ |
| July | 64.5 | 8,831 ft | 82.3 | 9,898 ft ⚠ |
| August | 62.6 | 8,714 ft | 80.4 | 9,786 ft ⚠ |
| September | 54.3 | 8,199 ft | 71.5 | 9,256 ft ⚠ |
| October | 42.8 | 7,467 ft | 57.3 | 8,386 ft ⚠ |
| November | 29.3 | 6,582 ft | 40.5 | 7,318 ft ▲ |
| December | 19.2 | 5,899 ft | 29.8 | 6,615 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 U61
DENSITY ALTITUDE high DA
Field elevation 6,900 ft — the air behaves like 9,880 ft.
- PRESSURE ALT
- 6,902 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
- 0U2 — Copper Basin
Mackay · elev 7,920 ft
- U62 — Mackay
Mackay · elev 5,892 ft
- U92 — Antelope Valley
Moore · elev 6,193 ft
- KSUN — Friedman Meml
Hailey · elev 5,320 ft
- U87 — Smiley Creek
Smiley Creek · elev 7,206 ft
- KLLJ — Challis
Challis · elev 5,076 ft
- U65 — Carey
Carey · elev 4,789 ft
- 2U7 — Stanley
Stanley · elev 6,403 ft
Frequently asked questions
How high does density altitude get at U61 in summer?
On a typical July afternoon — around 82 °F at the nearest NOAA normals station — density altitude at Twin Bridges reaches roughly 9,898 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 U61 on an average day?
It swings with the seasons: from roughly 5,886 ft at the coldest month's average temperature to about 8,831 ft at the warmest month's — all from a constant field elevation of 6,900 ft. The month-by-month table above carries the full year.
What is the field elevation of Twin Bridges?
6,900 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is U61 (FAA), in Ketchum, Idaho.