Short answer
In the standard atmosphere, air cools by 6.5 °C for every 1,000 m of height, about 3.6 °F per 1,000 ft. From a trailhead at 800 m and 14 °C, a summit at 2,300 m is estimated at 4.25 °C, about 4.3 °C. The NWS gives the dry-air rate as 9.8 °C per km. Real temperature profiles can differ, including temperature inversions.
In the standard atmosphere, air temperature falls by 6.5 °C for every 1,000 m of height. In imperial units that is about 3.6 °F per 1,000 ft. The figure is a standard-atmosphere model value, and the real temperature on a given day can be higher or lower. For a hike, the useful question is how much colder the summit will be than the trailhead you measured, and the answer depends on which rate of cooling applies to the air that day.
The standard rate: 6.5 °C per 1,000 m
NASA Glenn's Earth Atmosphere Model gives the temperature in the troposphere, from the surface to 11,000 m, as a linear function of height:
T = 15.04 − 0.00649 × h T = air temperature (°C), h = altitude (m)
The coefficient 0.00649 is 6.49 °C per 1,000 m, which is the standard rate of 6.5 °C per 1,000 m rounded to one decimal place. The equation starts at 15.04 °C at sea level and cools linearly. The table gives the standard temperature at several heights and the total fall from sea level.
| Altitude | Feet | Air temperature | In °F | Fall from 15 °C |
|---|---|---|---|---|
| 0 m | 0 ft | 15.0 °C | 59.1 °F | 0 °C |
| 1,000 m | 3,281 ft | 8.6 °C | 47.4 °F | 6.5 °C |
| 2,000 m | 6,562 ft | 2.1 °C | 35.7 °F | 13.0 °C |
| 3,000 m | 9,843 ft | −4.4 °C | 24.0 °F | 19.5 °C |
| 4,000 m | 13,123 ft | −10.9 °C | 12.3 °F | 26.0 °C |
| 5,000 m | 16,404 ft | −17.4 °C | 0.7 °F | 32.5 °C |
The feet column is each height multiplied by 3.2808, rounded to the nearest foot. Those heights are standard-atmosphere values, so they do not show a day's weather. They show the baseline that any local reading should be compared against.
Converting the rate to feet
Two steps convert 6.5 °C per 1,000 m into imperial units. First, 1,000 ft is 0.3048 km, so the rate per 1,000 ft in °C is 6.5 × 0.3048 = 1.98 °C. Second, a Celsius change becomes a Fahrenheit change by multiplying by 1.8: 1.98 × 1.8 = 3.57 °F. That is the "about 3.6 °F per 1,000 ft" figure.
The dry-air rate converts the same way: 9.8 × 0.3048 × 1.8 = 5.38 °F per 1,000 ft. The NWS glossary rounds the same rate to 5.5 °F per 1,000 ft; the exact conversion of 9.8 °C per km is 5.4 °F.
Dry air, saturated air and the rates in the altitude tool
The NWS glossary separates two rates. For a parcel of air that remains unsaturated as it rises, the dry adiabatic lapse rate is 9.8 °C per kilometre. The moist, or saturated, adiabatic lapse rate is different. The NWS describes it as "not a constant like the dry adiabatic lapse rate but is dependent on parcel temperature and pressure".
The altitude tool offers three rates. Its 6.5 option is the standard atmosphere. Its 9.8 option is the dry-air rate. Its 5 option approximates saturated air at about 5 °C per 1,000 m, and the tool notes that it varies with temperature, which matches the NWS point that the moist rate is not constant. Use 6.5 for a general estimate, 9.8 for rising dry air, and 5 only as a rough figure for saturated conditions.
Worked example: trailhead at 800 m and 14 °C, summit at 2,300 m
The height difference is 2,300 − 800 = 1,500 m, or 1.5 km. Multiply it by each rate and subtract from 14 °C:
at 6.5 °C per km: 14 − (6.5 × 1.5) = 14 − 9.75 = 4.25 °C at 9.8 °C per km: 14 − (9.8 × 1.5) = 14 − 14.7 = −0.7 °C at 5 °C per km: 14 − (5.0 × 1.5) = 14 − 7.5 = 6.5 °C
The altitude tool applies the same subtraction. Its estimate is the trailhead temperature minus the lapse rate times the height gained, in km: 14 − 6.5 × (2,300 − 800) ÷ 1,000 = 4.25 °C. The tool shows the rate you choose, so the three answers above are the range you can compare.
Adding the wind at the summit
Skin responds to the wind chill rather than the air temperature alone. At 4.25 °C in a 30 km/h wind, the wind chill is −0.9 °C. The Feels like tool takes temperatures in 0.5 °C steps, so its link uses 4.5 °C instead. At 4.5 °C and 30 km/h the wind chill is −0.6 °C, which is 5.1 °C below the air temperature (4.5 − (−0.6) = 5.1). The index applies here because the air is at or below 10 °C and the wind is above 4.8 km/h. Humidity does not enter the wind chill, and the wind chill guide shows the formula and its limits.
Inversions and the real profile
The lapse estimate assumes air temperature falls steadily with height. The NWS defines a temperature inversion as "a layer of the atmosphere in which air temperature increases with height", and a surface-based inversion is one whose base is at the ground. The NWS glossary says a nocturnal inversion can form overnight through radiational cooling of the surface, and that it "typically erodes quickly after sunrise".
In an inversion the summit can be warmer than the trailhead. A lapse estimate made from a cold trailhead then reads too cold at the top. The NWS glossary does not give a rule for how often this happens, so check the forecast for the day rather than assuming the standard profile.
Using the estimate on a route
Treat the estimate as a planning range, not a forecast for the summit. Read the trailhead temperature at the time you plan to start, because a morning reading and an afternoon reading describe different profiles. Where a forecast for the summit exists, use it in preference to the estimate.
A colder summit changes what you carry. For the clothing to carry, see the ten essentials. On the hot side of the same question, the heat index guide covers humid air at the trailhead. The pressure and boiling point at the same heights are in the boiling point guide. Set the time to turn back using a turnaround time, and do not extend it to reach a summit that is colder than the plan allowed for.
Common questions
How much colder is it per 1,000 ft?
In the standard atmosphere, about 3.6 °F per 1,000 ft. The arithmetic is 6.5 °C per 1,000 m × 0.3048 (1,000 ft in km) × 1.8, which gives 3.57 °F. Dry air that is rising cools faster, at 9.8 °C per km, which is about 5.4 °F per 1,000 ft.
What is the temperature at 3,000 m?
The standard atmosphere gives about −4.4 °C at 3,000 m, from 15.04 − 0.00649 × 3,000 = −4.4 °C. From a local reading, apply the rate to the height above that reading, not to sea level. The real temperature on a given day can differ from both figures.
Why can a summit be warmer than the trailhead?
During a temperature inversion, air temperature rises with height over a layer. The NWS notes that nocturnal inversions form overnight and typically erode quickly after sunrise. A cold valley in the early morning can sit under a warmer layer, so the lapse estimate can be too cold at the top.
Sources
- Earth Atmosphere Model, troposphere equation (NASA Glenn)
- Lapse rate (NWS glossary)
- Dry adiabatic lapse rate (NWS glossary)
- Inversion (NWS glossary)
Published 2 November 2026. Reviewed 2 November 2026. Sources support the figures quoted; they do not endorse Trailwright. Report a correction through the owner’s contact page.