St Johns, Michigan · field elev 680 ft
Density Altitude at Shady Lane (M99)
Shady Lane sits at 680 ft, and even a typical July afternoon (83 °F) only lifts density altitude to about 2,398 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 | 24.2 | −1,520 ft | 30.6 | −1,067 ft |
| February | 25.8 | −1,406 ft | 33.0 | −900 ft |
| March | 34.9 | −767 ft | 43.7 | −163 ft |
| April | 46.6 | 33 ft | 56.9 | 720 ft |
| May | 58.8 | 844 ft | 69.3 | 1,524 ft |
| June | 68.8 | 1,492 ft | 78.9 | 2,130 ft |
| July | 72.8 | 1,747 ft | 83.2 | 2,398 ft |
| August | 71.0 | 1,632 ft | 81.3 | 2,280 ft |
| September | 63.9 | 1,177 ft | 74.8 | 1,873 ft |
| October | 52.2 | 409 ft | 61.7 | 1,034 ft |
| November | 40.0 | −415 ft | 47.3 | 81 ft |
| December | 30.0 | −1,110 ft | 36.0 | −691 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 M99
DENSITY ALTITUDE
Field elevation 680 ft — the air behaves like 2,386 ft.
- PRESSURE ALT
- 681 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 Michigan fields
- 39T — Tripp Creek
St Johns · elev 717 ft
- 97G — Glowacki
St Johns · elev 775 ft
- 3S5 — Schiffer Acres
St Johns · elev 741 ft
- 4M4 — Shady Lawn Field
Bannister · elev 683 ft
- C57 — Millers Landing
Elsie · elev 757 ft
- 3F5 — Forest Hill
Westphalia · elev 772 ft
- 51C — Orban
Dewitt · elev 882 ft
- 41G — University Airpark
Bath · elev 856 ft
Frequently asked questions
How high does density altitude get at M99 in summer?
On a typical July afternoon — around 83 °F at the nearest NOAA normals station — density altitude at Shady Lane reaches roughly 2,398 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 M99 on an average day?
It swings with the seasons: from roughly −1,520 ft at the coldest month's average temperature to about 1,747 ft at the warmest month's — all from a constant field elevation of 680 ft. The month-by-month table above carries the full year.
What is the field elevation of Shady Lane?
680 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is M99 (FAA), in St Johns, Michigan.