Mattituck, New York · field elev 30 ft
Density Altitude at Mattituck (21N)
Mattituck sits at 30 ft, and even a typical July afternoon (82 °F) only lifts density altitude to about 1,517 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 | 30.4 | −1,895 ft | 38.2 | −1,349 ft |
| February | 32.0 | −1,782 ft | 40.2 | −1,211 ft |
| March | 38.3 | −1,342 ft | 47.0 | −746 ft |
| April | 47.8 | −692 ft | 56.8 | −90 ft |
| May | 57.7 | −30 ft | 67.1 | 583 ft |
| June | 67.0 | 577 ft | 75.3 | 1,108 ft |
| July | 73.3 | 981 ft | 81.8 | 1,517 ft |
| August | 72.9 | 956 ft | 81.4 | 1,492 ft |
| September | 65.6 | 486 ft | 74.4 | 1,051 ft |
| October | 54.8 | −223 ft | 63.6 | 356 ft |
| November | 44.6 | −909 ft | 53.1 | −336 ft |
| December | 35.8 | −1,516 ft | 43.3 | −998 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 21N
DENSITY ALTITUDE
Field elevation 30 ft — the air behaves like 1,529 ft.
- PRESSURE ALT
- 31 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 New York fields
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East Hampton · elev 55 ft
- KHWV — Brookhaven
Shirley · elev 81 ft
- 0B8 — Elizabeth Field
Fishers Island · elev 7 ft
- KMTP — Montauk
Montauk · elev 7 ft
- 23N — Bayport Aerodrome
Bayport · elev 39 ft
- KISP — Long Island Mac Arthur
New York · elev 99 ft
- KFRG — Republic
Farmingdale · elev 82 ft
Frequently asked questions
How high does density altitude get at 21N in summer?
On a typical July afternoon — around 82 °F at the nearest NOAA normals station — density altitude at Mattituck reaches roughly 1,517 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 21N on an average day?
It swings with the seasons: from roughly −1,895 ft at the coldest month's average temperature to about 981 ft at the warmest month's — all from a constant field elevation of 30 ft. The month-by-month table above carries the full year.
What is the field elevation of Mattituck?
30 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is 21N (FAA), in Mattituck, New York.