Port Townsend, Washington · field elev 110 ft
Density Altitude at Jefferson County International (0S9)
Jefferson County International sits at 110 ft, and even a typical August afternoon (73 °F) only lifts density altitude to about 1,066 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 | 42.4 | −960 ft | 46.4 | −688 ft |
| February | 43.4 | −892 ft | 48.6 | −539 ft |
| March | 46.2 | −701 ft | 52.1 | −304 ft |
| April | 50.4 | −418 ft | 57.5 | 55 ft |
| May | 55.2 | −97 ft | 63.1 | 422 ft |
| June | 59.4 | 180 ft | 67.9 | 733 ft |
| July | 62.8 | 403 ft | 72.6 | 1,035 ft |
| August | 63.3 | 435 ft | 73.1 | 1,066 ft |
| September | 59.5 | 187 ft | 68.0 | 740 ft |
| October | 52.2 | −297 ft | 58.2 | 101 ft |
| November | 45.7 | −735 ft | 50.1 | −438 ft |
| December | 41.8 | −1,001 ft | 45.3 | −762 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 0S9
DENSITY ALTITUDE
Field elevation 110 ft — the air behaves like 1,060 ft.
- PRESSURE ALT
- 111 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 Washington fields
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Langley · elev 271 ft
- W28 — Sequim Valley
Sequim · elev 151 ft
- 13W — Camano Island Airfield
Stanwood · elev 145 ft
- KPAE — Seattle Paine Field International
Everett · elev 607 ft
- 8W5 — Apex Airpark
Silverdale · elev 525 ft
- S31 — Lopez Island
Lopez · elev 209 ft
- KAWO — Arlington Municipal
Arlington · elev 142 ft
Frequently asked questions
How high does density altitude get at 0S9 in summer?
On a typical August afternoon — around 73 °F at the nearest NOAA normals station — density altitude at Jefferson County International reaches roughly 1,066 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 0S9 on an average day?
It swings with the seasons: from roughly −1,001 ft at the coldest month's average temperature to about 435 ft at the warmest month's — all from a constant field elevation of 110 ft. The month-by-month table above carries the full year.
What is the field elevation of Jefferson County International?
110 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is 0S9 (FAA), in Port Townsend, Washington.