Lopez, Washington · field elev 209 ft
Density Altitude at Lopez Island (S31)
Lopez Island sits at 209 ft, and even a typical August afternoon (73 °F) only lifts density altitude to about 1,201 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 | 42.1 | −858 ft | 47.1 | −517 ft |
| February | 42.5 | −830 ft | 48.5 | −423 ft |
| March | 45.5 | −626 ft | 52.6 | −148 ft |
| April | 49.1 | −382 ft | 57.4 | 171 ft |
| May | 54.0 | −54 ft | 63.7 | 584 ft |
| June | 58.2 | 224 ft | 68.4 | 887 ft |
| July | 61.2 | 421 ft | 72.4 | 1,143 ft |
| August | 61.6 | 447 ft | 73.3 | 1,201 ft |
| September | 58.0 | 210 ft | 68.1 | 868 ft |
| October | 51.2 | −241 ft | 58.5 | 243 ft |
| November | 45.4 | −633 ft | 51.0 | −255 ft |
| December | 41.6 | −892 ft | 46.3 | −571 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 S31
DENSITY ALTITUDE
Field elevation 209 ft — the air behaves like 1,182 ft.
- PRESSURE ALT
- 210 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
- KFHR — Friday Harbor
Friday Harbor · elev 113 ft
- 74S — Anacortes
Anacortes · elev 246 ft
- KORS — Orcas Island
Eastsound · elev 35 ft
- KOKH — Delaurentis
Oak Harbor · elev 193 ft
- KBVS — Skagit Regional
Burlington/Mount Vernon · elev 145 ft
- 13W — Camano Island Airfield
Stanwood · elev 145 ft
- KBLI — Bellingham International
Bellingham · elev 171 ft
- W28 — Sequim Valley
Sequim · elev 151 ft
Frequently asked questions
How high does density altitude get at S31 in summer?
On a typical August afternoon — around 73 °F at the nearest NOAA normals station — density altitude at Lopez Island reaches roughly 1,201 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 S31 on an average day?
It swings with the seasons: from roughly −892 ft at the coldest month's average temperature to about 447 ft at the warmest month's — all from a constant field elevation of 209 ft. The month-by-month table above carries the full year.
What is the field elevation of Lopez Island?
209 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is S31 (FAA), in Lopez, Washington.