Lacon, Illinois · field elev 585 ft
Density Altitude at Marshall County (C75)
Marshall County sits at 585 ft, and even a typical July afternoon (87 °F) only lifts density altitude to about 2,516 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 | 25.9 | −1,518 ft | 33.8 | −962 ft |
| February | 29.9 | −1,235 ft | 38.3 | −651 ft |
| March | 41.4 | −438 ft | 51.4 | 238 ft |
| April | 52.9 | 338 ft | 64.5 | 1,098 ft |
| May | 63.3 | 1,021 ft | 75.0 | 1,769 ft |
| June | 72.8 | 1,630 ft | 84.4 | 2,356 ft |
| July | 76.0 | 1,832 ft | 87.0 | 2,516 ft |
| August | 74.3 | 1,725 ft | 85.6 | 2,430 ft |
| September | 67.4 | 1,285 ft | 79.6 | 2,058 ft |
| October | 55.0 | 477 ft | 66.6 | 1,234 ft |
| November | 41.9 | −404 ft | 51.2 | 224 ft |
| December | 30.8 | −1,172 ft | 38.3 | −651 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 C75
DENSITY ALTITUDE
Field elevation 585 ft — the air behaves like 2,516 ft.
- PRESSURE ALT
- 586 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
- 3MY — Mount Hawley Auxiliary
Peoria · elev 793 ft
- KVYS — Illinois Valley Regional-Walter A Duncan Field
Peru · elev 654 ft
- KPIA — General Downing - Peoria International
Peoria · elev 661 ft
- KEZI — Kewanee Municipal
Kewanee · elev 858 ft
- C15 — Pekin Municipal
Pekin · elev 530 ft
- 2C6 — Tri-County
Yates City · elev 661 ft
- KPNT — Pontiac Municipal
Pontiac · elev 666 ft
- 8N2 — Skydive Chicago
Ottawa · elev 616 ft
Frequently asked questions
How high does density altitude get at C75 in summer?
On a typical July afternoon — around 87 °F at the nearest NOAA normals station — density altitude at Marshall County reaches roughly 2,516 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 C75 on an average day?
It swings with the seasons: from roughly −1,518 ft at the coldest month's average temperature to about 1,832 ft at the warmest month's — all from a constant field elevation of 585 ft. The month-by-month table above carries the full year.
What is the field elevation of Marshall County?
585 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is C75 (FAA), in Lacon, Illinois.