Rockford, Illinois · field elev 741 ft
Density Altitude at Cottonwood (1C8)
Cottonwood sits at 741 ft, and even a typical July afternoon (84 °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 | 21.8 | −1,616 ft | 29.1 | −1,097 ft |
| February | 25.6 | −1,344 ft | 33.4 | −795 ft |
| March | 37.3 | −525 ft | 46.5 | 102 ft |
| April | 49.1 | 277 ft | 59.7 | 979 ft |
| May | 60.4 | 1,024 ft | 71.2 | 1,720 ft |
| June | 70.1 | 1,650 ft | 80.7 | 2,317 ft |
| July | 73.8 | 1,885 ft | 83.9 | 2,516 ft |
| August | 71.9 | 1,764 ft | 82.0 | 2,398 ft |
| September | 64.4 | 1,284 ft | 75.3 | 1,979 ft |
| October | 52.0 | 471 ft | 62.3 | 1,148 ft |
| November | 38.8 | −422 ft | 47.1 | 143 ft |
| December | 27.3 | −1,224 ft | 34.3 | −733 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 1C8
DENSITY ALTITUDE
Field elevation 741 ft — the air behaves like 2,522 ft.
- PRESSURE ALT
- 742 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
- KRFD — Chicago/Rockford International
Chicago/Rockford · elev 742 ft
- C77 — Poplar Grove
Poplar Grove · elev 857 ft
- C55 — Ogle County
Mount Morris · elev 929 ft
- KFEP — Albertus
Freeport · elev 859 ft
- 0C0 — Dacy
Harvard · elev 913 ft
- KRPJ — Rochelle Municipal/Koritz Field
Rochelle · elev 781 ft
- KDKB — De Kalb Taylor Municipal
De Kalb · elev 913 ft
- C73 — Dixon Municipal-Charles R Walgreen Field
Dixon · elev 785 ft
Frequently asked questions
How high does density altitude get at 1C8 in summer?
On a typical July afternoon — around 84 °F at the nearest NOAA normals station — density altitude at Cottonwood 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 1C8 on an average day?
It swings with the seasons: from roughly −1,616 ft at the coldest month's average temperature to about 1,885 ft at the warmest month's — all from a constant field elevation of 741 ft. The month-by-month table above carries the full year.
What is the field elevation of Cottonwood?
741 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is 1C8 (FAA), in Rockford, Illinois.