Alton/St Louis, Illinois · field elev 544 ft
Density Altitude at St Louis Regional (KALN)
St Louis Regional sits at 544 ft, and even a typical July afternoon (87 °F) only lifts density altitude to about 2,485 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 | 30.3 | −1,259 ft | 39.0 | −653 ft |
| February | 34.5 | −965 ft | 43.7 | −332 ft |
| March | 44.1 | −305 ft | 53.5 | 327 ft |
| April | 55.6 | 466 ft | 66.1 | 1,151 ft |
| May | 65.6 | 1,119 ft | 75.0 | 1,719 ft |
| June | 74.6 | 1,694 ft | 83.7 | 2,263 ft |
| July | 78.3 | 1,927 ft | 87.3 | 2,485 ft |
| August | 76.6 | 1,820 ft | 86.0 | 2,405 ft |
| September | 70.0 | 1,402 ft | 80.1 | 2,039 ft |
| October | 57.9 | 618 ft | 67.9 | 1,267 ft |
| November | 45.4 | −216 ft | 54.3 | 380 ft |
| December | 35.3 | −909 ft | 43.5 | −345 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 KALN
DENSITY ALTITUDE
Field elevation 544 ft — the air behaves like 2,466 ft.
- PRESSURE ALT
- 545 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 Illinois fields
- KCPS — St Louis Downtown
Cahokia/St Louis · elev 413 ft
- H07 — Highland-Winet
Highland · elev 537 ft
- KBLV — Scott AFB/Midamerica St Louis
Belleville · elev 459 ft
- 3LF — Litchfield Municipal
Litchfield · elev 691 ft
- KGRE — Greenville
Greenville · elev 541 ft
- 5K1 — Zelmer Meml Airpark Inc
Palmyra · elev 663 ft
- KVLA — Vandalia Municipal
Vandalia · elev 537 ft
- KSAR — Sparta Community-Hunter Field
Sparta · elev 538 ft
Frequently asked questions
How high does density altitude get at KALN in summer?
On a typical July afternoon — around 87 °F at the nearest NOAA normals station — density altitude at St Louis Regional reaches roughly 2,485 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 KALN on an average day?
It swings with the seasons: from roughly −1,259 ft at the coldest month's average temperature to about 1,927 ft at the warmest month's — all from a constant field elevation of 544 ft. The month-by-month table above carries the full year.
What is the field elevation of St Louis Regional?
544 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is KALN (ICAO) / ALN (FAA), in Alton/St Louis, Illinois.