Marysville, Ohio · field elev 1,021 ft
Density Altitude at Union County (KMRT)
Union County sits at 1,021 ft, and even a typical July afternoon (85 °F) only lifts density altitude to about 2,919 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 | 27.8 | −838 ft | 35.0 | −335 ft |
| February | 30.9 | −620 ft | 38.9 | −66 ft |
| March | 40.2 | 23 ft | 49.6 | 657 ft |
| April | 52.0 | 817 ft | 63.0 | 1,538 ft |
| May | 62.7 | 1,519 ft | 73.6 | 2,215 ft |
| June | 71.2 | 2,063 ft | 81.7 | 2,721 ft |
| July | 74.7 | 2,284 ft | 84.9 | 2,919 ft |
| August | 73.0 | 2,177 ft | 83.5 | 2,832 ft |
| September | 66.1 | 1,738 ft | 77.5 | 2,460 ft |
| October | 54.4 | 976 ft | 65.0 | 1,667 ft |
| November | 42.3 | 166 ft | 50.9 | 744 ft |
| December | 32.9 | −481 ft | 39.6 | −18 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 KMRT
DENSITY ALTITUDE
Field elevation 1,021 ft — the air behaves like 2,925 ft.
- PRESSURE ALT
- 1,022 ft
- ISA DEVIATION
- —
- RULE-OF-THUMB DA
- —
- AIR DENSITY INDEX
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- AIR DENSITY
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- WATER · GRAINS/LB
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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 Ohio fields
- KDLZ — Delaware Municipal/Jim Moore Field
Delaware · elev 945 ft
- 5E9 — Packer
Radnor · elev 918 ft
- KOSU — Ohio State University
Columbus · elev 906 ft
- 38I — Cook
Urbana · elev 1,150 ft
- KUYF — Madison County
London · elev 1,082 ft
- I74 — Grimes Field
Urbana · elev 1,068 ft
- KTZR — Bolton Field
Columbus · elev 904 ft
- KEDJ — Bellefontaine Regional
Bellefontaine · elev 1,122 ft
Frequently asked questions
How high does density altitude get at KMRT in summer?
On a typical July afternoon — around 85 °F at the nearest NOAA normals station — density altitude at Union County reaches roughly 2,919 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 KMRT on an average day?
It swings with the seasons: from roughly −838 ft at the coldest month's average temperature to about 2,284 ft at the warmest month's — all from a constant field elevation of 1,021 ft. The month-by-month table above carries the full year.
What is the field elevation of Union County?
1,021 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is KMRT (ICAO) / MRT (FAA), in Marysville, Ohio.