Decatur, Illinois · field elev 682 ft
Density Altitude at Decatur (KDEC)
Decatur sits at 682 ft, and even a typical July afternoon (86 °F) only lifts density altitude to about 2,561 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 | 27.4 | −1,290 ft | 34.7 | −779 ft |
| February | 31.6 | −995 ft | 39.8 | −427 ft |
| March | 42.1 | −269 ft | 51.9 | 391 ft |
| April | 53.1 | 471 ft | 63.9 | 1,179 ft |
| May | 63.9 | 1,179 ft | 74.4 | 1,850 ft |
| June | 72.7 | 1,743 ft | 83.0 | 2,388 ft |
| July | 75.7 | 1,932 ft | 85.8 | 2,561 ft |
| August | 73.7 | 1,806 ft | 84.3 | 2,468 ft |
| September | 67.0 | 1,379 ft | 78.9 | 2,133 ft |
| October | 55.2 | 610 ft | 66.1 | 1,321 ft |
| November | 42.7 | −228 ft | 51.3 | 351 ft |
| December | 32.4 | −939 ft | 39.7 | −433 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 KDEC
DENSITY ALTITUDE
Field elevation 682 ft — the air behaves like 2,573 ft.
- PRESSURE ALT
- 683 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
- 2H0 — Shelby County
Shelbyville · elev 619 ft
- K96 — Tuscola
Tuscola · elev 665 ft
- KTAZ — Taylorville Municipal
Taylorville · elev 622 ft
- KAAA — Logan County
Lincoln · elev 594 ft
- KCMI — University Of Illinois/Willard
Champaign/Urbana · elev 755 ft
- KMTO — Coles County Meml
Mattoon/Charleston · elev 722 ft
- C16 — Frasca Field
Urbana · elev 735 ft
- KSPI — Abraham Lincoln Capital
Springfield · elev 598 ft
Frequently asked questions
How high does density altitude get at KDEC in summer?
On a typical July afternoon — around 86 °F at the nearest NOAA normals station — density altitude at Decatur reaches roughly 2,561 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 KDEC on an average day?
It swings with the seasons: from roughly −1,290 ft at the coldest month's average temperature to about 1,932 ft at the warmest month's — all from a constant field elevation of 682 ft. The month-by-month table above carries the full year.
What is the field elevation of Decatur?
682 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is KDEC (ICAO) / DEC (FAA), in Decatur, Illinois.