Highgate, Vermont · field elev 228 ft
Density Altitude at Franklin County State (KFSO)
Franklin County State sits at 228 ft, and even a typical July afternoon (79 °F) only lifts density altitude to about 1,609 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 | 16.7 | −2,630 ft | 25.1 | −2,023 ft |
| February | 19.4 | −2,433 ft | 28.5 | −1,781 ft |
| March | 28.4 | −1,788 ft | 36.8 | −1,199 ft |
| April | 42.7 | −793 ft | 52.0 | −164 ft |
| May | 56.0 | 102 ft | 65.7 | 737 ft |
| June | 65.1 | 698 ft | 74.4 | 1,294 ft |
| July | 70.1 | 1,020 ft | 79.4 | 1,609 ft |
| August | 68.0 | 885 ft | 77.2 | 1,471 ft |
| September | 60.2 | 378 ft | 69.4 | 975 ft |
| October | 47.9 | −440 ft | 56.1 | 108 ft |
| November | 36.8 | −1,199 ft | 44.0 | −704 ft |
| December | 25.0 | −2,030 ft | 32.3 | −1,513 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 KFSO
DENSITY ALTITUDE
Field elevation 228 ft — the air behaves like 1,584 ft.
- PRESSURE ALT
- 229 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 Vermont fields
- KBTV — Patrick Leahy Burlington International
Burlington · elev 335 ft
- KMVL — Morrisville-Stowe State
Morrisville · elev 733 ft
- VT8 — Shelburne
Shelburne · elev 325 ft
- KEFK — Northeast Kingdom International
Newport · elev 934 ft
- B06 — Basin Harbor
Vergennes · elev 124 ft
- KMPV — Edward F Knapp State
Barre/Montpelier · elev 1,166 ft
- 0B7 — Warren-Sugarbush
Warren · elev 1,470 ft
- KCDA — Caledonia County
Lyndonville · elev 1,188 ft
Frequently asked questions
How high does density altitude get at KFSO in summer?
On a typical July afternoon — around 79 °F at the nearest NOAA normals station — density altitude at Franklin County State reaches roughly 1,609 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 KFSO on an average day?
It swings with the seasons: from roughly −2,630 ft at the coldest month's average temperature to about 1,020 ft at the warmest month's — all from a constant field elevation of 228 ft. The month-by-month table above carries the full year.
What is the field elevation of Franklin County State?
228 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is KFSO (ICAO) / FSO (FAA), in Highgate, Vermont.