Atwater, California · field elev 190 ft
Density Altitude at Castle (KMER)
Castle sits at 190 ft, and even a typical July afternoon (95 °F) only lifts density altitude to about 2,511 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 | 45.5 | −649 ft | 54.1 | −71 ft |
| February | 49.9 | −352 ft | 60.6 | 358 ft |
| March | 54.4 | −51 ft | 66.5 | 742 ft |
| April | 59.2 | 266 ft | 73.0 | 1,158 ft |
| May | 66.8 | 761 ft | 81.9 | 1,719 ft |
| June | 73.2 | 1,171 ft | 89.3 | 2,176 ft |
| July | 78.3 | 1,493 ft | 94.8 | 2,511 ft |
| August | 77.0 | 1,412 ft | 93.8 | 2,451 ft |
| September | 72.7 | 1,139 ft | 89.3 | 2,176 ft |
| October | 63.6 | 554 ft | 78.6 | 1,512 ft |
| November | 52.6 | −171 ft | 64.5 | 612 ft |
| December | 45.5 | −649 ft | 54.7 | −31 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 KMER
DENSITY ALTITUDE
Field elevation 190 ft — the air behaves like 2,523 ft.
- PRESSURE ALT
- 191 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 California fields
- KMCE — Merced Yosemite Regional
Merced · elev 155 ft
- O15 — Turlock Municipal
Turlock · elev 161 ft
- 3O1 — Gustine
Gustine · elev 79 ft
- 2O6 — Chowchilla
Chowchilla · elev 243 ft
- KMOD — Modesto City-County-Harry Sham Field
Modesto · elev 99 ft
- KLSN — Los Banos Municipal
Los Banos · elev 121 ft
- O27 — Oakdale
Oakdale · elev 237 ft
- KMPI — Mariposa-Yosemite
Mariposa · elev 2,254 ft
Frequently asked questions
How high does density altitude get at KMER in summer?
On a typical July afternoon — around 95 °F at the nearest NOAA normals station — density altitude at Castle reaches roughly 2,511 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 KMER on an average day?
It swings with the seasons: from roughly −649 ft at the coldest month's average temperature to about 1,493 ft at the warmest month's — all from a constant field elevation of 190 ft. The month-by-month table above carries the full year.
What is the field elevation of Castle?
190 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is KMER (ICAO) / MER (FAA), in Atwater, California.