Smithfield, North Carolina · field elev 164 ft
Density Altitude at Johnston Regional (KJNX)
Johnston Regional sits at 164 ft, and even a typical July afternoon (92 °F) only lifts density altitude to about 2,291 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 | 42.5 | −886 ft | 53.6 | −137 ft |
| February | 45.2 | −702 ft | 57.0 | 89 ft |
| March | 51.9 | −250 ft | 64.5 | 580 ft |
| April | 60.8 | 339 ft | 74.1 | 1,196 ft |
| May | 69.2 | 883 ft | 81.0 | 1,631 ft |
| June | 77.1 | 1,386 ft | 88.3 | 2,083 ft |
| July | 81.2 | 1,643 ft | 91.7 | 2,291 ft |
| August | 78.9 | 1,499 ft | 89.3 | 2,144 ft |
| September | 73.3 | 1,145 ft | 83.6 | 1,793 ft |
| October | 62.2 | 430 ft | 74.3 | 1,209 ft |
| November | 51.7 | −264 ft | 64.4 | 574 ft |
| December | 45.2 | −702 ft | 56.7 | 69 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 KJNX
DENSITY ALTITUDE
Field elevation 164 ft — the air behaves like 2,309 ft.
- PRESSURE ALT
- 165 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 North Carolina fields
- 5W5 — Southern Wake Regional
Raleigh · elev 243 ft
- KHRJ — Harnett Regional Jetport
Erwin · elev 202 ft
- KGWW — Wayne Exec Jetport
Goldsboro · elev 134 ft
- W03 — Wilson Industrial Air Center
Wilson · elev 160 ft
- W40 — Mount Olive Municipal
Mount Olive · elev 167 ft
- KRDU — Raleigh-Durham International
Raleigh/Durham · elev 435 ft
- KLHZ — Triangle North Exec
Louisburg · elev 368 ft
- KRWI — Rocky Mount/Wilson Regional
Rocky Mount · elev 158 ft
Frequently asked questions
How high does density altitude get at KJNX in summer?
On a typical July afternoon — around 92 °F at the nearest NOAA normals station — density altitude at Johnston Regional reaches roughly 2,291 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 KJNX on an average day?
It swings with the seasons: from roughly −886 ft at the coldest month's average temperature to about 1,643 ft at the warmest month's — all from a constant field elevation of 164 ft. The month-by-month table above carries the full year.
What is the field elevation of Johnston Regional?
164 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is KJNX (ICAO) / JNX (FAA), in Smithfield, North Carolina.