Montague, California · field elev 2,651 ft
Density Altitude at Siskiyou County (KSIY)
From a field elevation of 2,651 ft, a typical July afternoon at Siskiyou County (93 °F) raises density altitude to about 5,413 ft — solidly into the range where performance charts deserve a close read.
Typical density altitude by month
| Month | Avg temp °F | DA at avg temp | Afternoon high °F | DA on a typical afternoon |
|---|---|---|---|---|
| January | 36.7 | 1,810 ft | 47.2 | 2,515 ft |
| February | 39.8 | 2,020 ft | 52.5 | 2,863 ft |
| March | 44.4 | 2,329 ft | 58.2 | 3,234 ft |
| April | 48.9 | 2,627 ft | 63.7 | 3,586 ft |
| May | 57.2 | 3,169 ft | 73.7 | 4,215 ft |
| June | 64.9 | 3,662 ft | 82.8 | 4,775 ft |
| July | 74.0 | 4,234 ft | 93.4 | 5,413 ft ▲ |
| August | 72.4 | 4,134 ft | 92.2 | 5,342 ft ▲ |
| September | 64.9 | 3,662 ft | 84.4 | 4,873 ft |
| October | 52.8 | 2,883 ft | 69.6 | 3,959 ft |
| November | 41.9 | 2,161 ft | 54.2 | 2,974 ft |
| December | 35.8 | 1,749 ft | 45.7 | 2,415 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 KSIY
DENSITY ALTITUDE caution
Field elevation 2,651 ft — the air behaves like 5,389 ft.
- PRESSURE ALT
- 2,653 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
- 1O5 — Montague-Yreka Rohrer Field
Montague · elev 2,527 ft
- O46 — Weed
Weed · elev 2,943 ft
- A30 — Scott Valley
Fort Jones · elev 2,728 ft
- A32 — Butte Valley
Dorris · elev 4,243 ft
- 1O6 — Dunsmuir Municipal-Mott
Dunsmuir · elev 3,261 ft
- 36S — Happy Camp
Happy Camp · elev 1,209 ft
- O86 — Trinity Center
Trinity Center · elev 2,390 ft
- O81 — Tulelake Municipal
Tulelake · elev 4,049 ft
Frequently asked questions
How high does density altitude get at KSIY in summer?
On a typical July afternoon — around 93 °F at the nearest NOAA normals station — density altitude at Siskiyou County reaches roughly 5,413 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 KSIY on an average day?
It swings with the seasons: from roughly 1,749 ft at the coldest month's average temperature to about 4,234 ft at the warmest month's — all from a constant field elevation of 2,651 ft. The month-by-month table above carries the full year.
What is the field elevation of Siskiyou County?
2,651 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is KSIY (ICAO) / SIY (FAA), in Montague, California.