Paritian

Science

Cloud Base Calculator (from Temperature and Dew Point)

Estimated height of the base of cumulus clouds from the air temperature and dew point at the ground.

Results

Cloud base above the ground 1000 m
Cloud base in feet 3281 ft
Cloud base above sea level 1000 m
Temperature at the cloud base 10.2 °C
How it changes
Cloud base above the groundAir temperature at the ground 12 – 32. Cloud base above the ground: 0 → 2500Cloud base above the ground0500100015002000250015202530Air temperature at the ground (°C)

The dashed line marks the value you entered.

What this tool does

Rising air cools by about 9.8 °C per kilometre while its dew point drops by only about 1.8 °C per kilometre, so the two meet — and cloud forms — roughly 125 metres up for every degree of difference at the ground. That is the old glider pilots' and meteorologists' rule of thumb, and it works best on sunny afternoons with fair-weather cumulus. It does not apply to layered cloud from approaching fronts, and a dew point equal to the temperature means fog or cloud at ground level.

Formula

h ≈ 125 m × (T − T_d)

Variables

SymbolMeaningUnit
tAir temperature at the ground°C
tdDew point°C
elElevation of the placem
CBCloud base above the groundm
FTCloud base in feetft
AMCloud base above sea levelm
TCTemperature at the cloud base°C

Worked example

  • Air temperature at the ground20 °C
  • Dew point12 °C
  • Elevation of the place0 m
  • Cloud base above the ground1000 m
  • Cloud base in feet3281 ft
  • Cloud base above sea level1000 m
  • Temperature at the cloud base10.2 °C

Limitations

  • The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
  • The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.