Forsyth, Montana · field elev 2,729 ft
Density Altitude at Tillitt Field (1S3)
From a field elevation of 2,729 ft, a typical July afternoon at Tillitt Field (88 °F) raises density altitude to about 5,185 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 | 21.9 | 883 ft | 33.7 | 1,703 ft |
| February | 25.7 | 1,150 ft | 38.0 | 1,995 ft |
| March | 36.3 | 1,880 ft | 49.3 | 2,750 ft |
| April | 46.1 | 2,538 ft | 59.2 | 3,394 ft |
| May | 55.8 | 3,174 ft | 68.8 | 4,004 ft |
| June | 65.2 | 3,777 ft | 78.5 | 4,607 ft |
| July | 73.1 | 4,273 ft | 88.0 | 5,185 ft ▲ |
| August | 71.1 | 4,148 ft | 86.5 | 5,094 ft ▲ |
| September | 60.5 | 3,477 ft | 75.4 | 4,416 ft |
| October | 46.8 | 2,585 ft | 60.0 | 3,445 ft |
| November | 33.9 | 1,716 ft | 46.1 | 2,538 ft |
| December | 24.0 | 1,031 ft | 35.4 | 1,819 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 1S3
DENSITY ALTITUDE caution
Field elevation 2,729 ft — the air behaves like 5,185 ft.
- PRESSURE ALT
- 2,731 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
- 6U7 — Hysham
Hysham · elev 2,624 ft
- M46 — Colstrip
Colstrip · elev 3,428 ft
- KMLS — Frank Wiley Field
Miles City · elev 2,634 ft
- 3U4 — St Labre Mission
Ashland · elev 2,909 ft
- 00U — Big Horn County
Hardin · elev 3,025 ft
- 8U1 — Sand Springs Strip
Sand Springs · elev 3,180 ft
- 1M6 — Stevens Ranch
Ashland · elev 3,300 ft
- 8U6 — Terry
Terry · elev 2,283 ft
Frequently asked questions
How high does density altitude get at 1S3 in summer?
On a typical July afternoon — around 88 °F at the nearest NOAA normals station — density altitude at Tillitt Field reaches roughly 5,185 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 1S3 on an average day?
It swings with the seasons: from roughly 883 ft at the coldest month's average temperature to about 4,273 ft at the warmest month's — all from a constant field elevation of 2,729 ft. The month-by-month table above carries the full year.
What is the field elevation of Tillitt Field?
2,729 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is 1S3 (FAA), in Forsyth, Montana.