Cloud Base Height Estimator

Estimate convective cloud base using temperature and dewpoint spread.

Same units as temperature

How It Works

Temperature decreases about 2C per 1000 ft, while dewpoint decreases about 0.5C per 1000 ft. Clouds form where they meet.

Rule of thumb: Cloud base (ft AGL) = Spread (C) x 400

Spread (F): Multiply spread by 222

Spread Interpretation

  • 0-3C: Fog/mist likely, low ceilings
  • 3-6C: Clouds possible, monitor
  • 6-10C: Fair weather cumulus likely
  • >10C: High cloud bases, dry conditions