Boulder, Montana · field elev 4,968 ft
Density Altitude at Boulder (3U9)
From a field elevation of 4,968 ft, a typical July afternoon at Boulder (83 °F) raises density altitude to about 7,571 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 | 23.5 | 3,790 ft | 35.0 | 4,570 ft |
| February | 25.9 | 3,954 ft | 37.8 | 4,757 ft |
| March | 33.8 | 4,490 ft | 46.8 | 5,348 ft ▲ |
| April | 40.7 | 4,949 ft | 54.5 | 5,843 ft ▲ |
| May | 49.4 | 5,516 ft | 63.6 | 6,418 ft ▲ |
| June | 57.2 | 6,015 ft | 72.0 | 6,937 ft ▲ |
| July | 65.4 | 6,530 ft | 82.5 | 7,571 ft ▲ |
| August | 64.1 | 6,449 ft | 82.0 | 7,541 ft ▲ |
| September | 55.0 | 5,875 ft | 71.9 | 6,930 ft ▲ |
| October | 42.6 | 5,074 ft | 57.4 | 6,028 ft ▲ |
| November | 30.5 | 4,267 ft | 42.4 | 5,060 ft ▲ |
| December | 22.5 | 3,721 ft | 33.6 | 4,476 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 3U9
DENSITY ALTITUDE caution
Field elevation 4,968 ft — the air behaves like 7,601 ft.
- PRESSURE ALT
- 4,970 ft
- ISA DEVIATION
- —
- RULE-OF-THUMB DA
- —
- AIR DENSITY INDEX
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- 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
- KBTM — Bert Mooney
Butte · elev 5,551 ft
- KHLN — Helena Regional
Helena · elev 3,877 ft
- 8U9 — Canyon Ferry
Townsend · elev 3,840 ft
- 8U8 — Townsend
Townsend · elev 3,897 ft
- 38S — Deer Lodge-City-County
Deer Lodge · elev 4,693 ft
- 9S5 — Three Forks
Three Forks · elev 4,089 ft
- 3U3 — Bowman Field
Anaconda · elev 5,034 ft
- KRVF — Ruby Valley Field
Twin Bridges · elev 4,789 ft
Frequently asked questions
How high does density altitude get at 3U9 in summer?
On a typical July afternoon — around 83 °F at the nearest NOAA normals station — density altitude at Boulder reaches roughly 7,571 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 3U9 on an average day?
It swings with the seasons: from roughly 3,721 ft at the coldest month's average temperature to about 6,530 ft at the warmest month's — all from a constant field elevation of 4,968 ft. The month-by-month table above carries the full year.
What is the field elevation of Boulder?
4,968 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is 3U9 (FAA), in Boulder, Montana.