Marathon, Florida · field elev 7 ft
Density Altitude at The Florida Keys Marathon International (KMTH)
The Florida Keys Marathon International sits at 7 ft, and even a typical August afternoon (92 °F) only lifts density altitude to about 2,094 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 | 70.0 | 742 ft | 75.8 | 1,112 ft |
| February | 72.3 | 889 ft | 78.1 | 1,257 ft |
| March | 74.6 | 1,035 ft | 80.7 | 1,420 ft |
| April | 78.3 | 1,269 ft | 84.1 | 1,632 ft |
| May | 81.7 | 1,483 ft | 87.5 | 1,842 ft |
| June | 84.4 | 1,651 ft | 90.3 | 2,014 ft |
| July | 85.2 | 1,700 ft | 90.9 | 2,051 ft |
| August | 85.6 | 1,725 ft | 91.6 | 2,094 ft |
| September | 84.2 | 1,638 ft | 89.9 | 1,990 ft |
| October | 81.0 | 1,439 ft | 86.2 | 1,762 ft |
| November | 76.0 | 1,124 ft | 81.2 | 1,451 ft |
| December | 72.7 | 915 ft | 77.9 | 1,244 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 KMTH
DENSITY ALTITUDE
Field elevation 7 ft — the air behaves like 2,118 ft.
- PRESSURE ALT
- 8 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 Florida fields
- KEYW — Key West International
Key West · elev 3 ft
- X51 — Miami Homestead General Aviation
Homestead · elev 7 ft
- KTMB — Miami Exec
Miami · elev 10 ft
- KTNT — Dade-Collier Training And Transition
Miami · elev 13 ft
- X01 — Everglades Airpark
Everglades City · elev 4 ft
- KMIA — Miami International
Miami · elev 9 ft
- KOPF — Miami-Opa Locka Exec
Miami · elev 8 ft
- KMKY — Marco Island Exec
Marco Island · elev 5 ft
Frequently asked questions
How high does density altitude get at KMTH in summer?
On a typical August afternoon — around 92 °F at the nearest NOAA normals station — density altitude at The Florida Keys Marathon International reaches roughly 2,094 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 KMTH on an average day?
It swings with the seasons: from roughly 742 ft at the coldest month's average temperature to about 1,725 ft at the warmest month's — all from a constant field elevation of 7 ft. The month-by-month table above carries the full year.
What is the field elevation of The Florida Keys Marathon International?
7 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is KMTH (ICAO) / MTH (FAA), in Marathon, Florida.