Jacksonville, Florida · field elev 86 ft
Density Altitude at Herlong Recreational (KHEG)
Herlong Recreational sits at 86 ft, and even a typical July afternoon (92 °F) only lifts density altitude to about 2,196 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 | 53.7 | −227 ft | 66.4 | 607 ft |
| February | 57.0 | −8 ft | 69.9 | 833 ft |
| March | 61.6 | 295 ft | 75.6 | 1,196 ft |
| April | 67.4 | 672 ft | 80.9 | 1,529 ft |
| May | 73.8 | 1,082 ft | 86.4 | 1,871 ft |
| June | 79.4 | 1,435 ft | 90.0 | 2,092 ft |
| July | 81.6 | 1,573 ft | 91.7 | 2,196 ft |
| August | 81.5 | 1,567 ft | 91.1 | 2,160 ft |
| September | 78.5 | 1,379 ft | 88.3 | 1,988 ft |
| October | 70.3 | 858 ft | 81.6 | 1,573 ft |
| November | 61.4 | 282 ft | 73.7 | 1,075 ft |
| December | 56.4 | −47 ft | 68.4 | 736 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 KHEG
DENSITY ALTITUDE
Field elevation 86 ft — the air behaves like 2,215 ft.
- PRESSURE ALT
- 87 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
- KVQQ — Cecil
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- KJAX — Jacksonville International
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- KCRG — Jacksonville Exec At Craig
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- 01J — Hilliard Airpark
Hilliard · elev 59 ft
- KFHB — Fernandina Beach Municipal
Fernandina Beach · elev 16 ft
- 42J — Keystone Heights
Keystone Heights · elev 196 ft
- KSGJ — St Augustine
St Augustine · elev 10 ft
- 28J — Palatka Municipal/Lt Kay Larkin Field
Palatka · elev 48 ft
Frequently asked questions
How high does density altitude get at KHEG in summer?
On a typical July afternoon — around 92 °F at the nearest NOAA normals station — density altitude at Herlong Recreational reaches roughly 2,196 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 KHEG on an average day?
It swings with the seasons: from roughly −227 ft at the coldest month's average temperature to about 1,573 ft at the warmest month's — all from a constant field elevation of 86 ft. The month-by-month table above carries the full year.
What is the field elevation of Herlong Recreational?
86 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is KHEG (ICAO) / HEG (FAA), in Jacksonville, Florida.