Cloud Ceiling Estimator
Estimate cloud-base height from surface temperature and dew point — useful for ridge-walking decisions.
Inputs
Result
A natural placement between the calculator and the explanation.
What this solves — and what it doesn't
Cloud base is roughly where the air cools enough for water vapor to condense — i.e., where temperature equals the dew point. A back-of-envelope rule: cloud base in meters = 125 × (temperature − dew point). A lapse-rate correction makes it more accurate. The result tells you whether your planned ridge will be in cloud or in sun.
How to read the result
Compare the estimated cloud base to your ridge elevation. If cloud base is below the ridge, expect clouds and reduced visibility on the ridge. If it’s well above, expect a clear traverse.
Storm cells can lower cloud base by 1,000+ m. Check this on the morning of a ridge walk, not the night before.
Limitations
- Assumes dry adiabatic lapse rate. Real atmosphere is often non-standard.
- Doesn’t model inversions (when air cools slowly).
- Doesn’t distinguish between stable or convective clouds.
Frequently asked questions
What is a temperature inversion?
A layer of warm air above cold air, which traps moisture below. Common in valleys at night. Cloud base can be very different than the rule predicts.
How do I measure dew point?
A sling psychrometer (wet/dry bulb) is the field method. Or watch for the temperature at which condensation forms on a metal surface.
Why does this matter for ridges?
On a ridge walk, low cloud = whiteout + navigation difficulty. Knowing cloud base helps you decide whether to commit.