Cumulus Clouds
Fair Weather Clouds ☁️
Altitude
0 - 6,500 feet (0 - 2 km)
Low-altitude clouds
Conditions
Fair weather, sunny
Most common daytime cloud
Precipitation
None or light
No precipitation typical
What Are Cumulus Clouds?
Cumulus clouds are puffy, white clouds with flat bases that look like floating cotton balls. They are the most recognizable cloud type and typically indicate fair weather. Cumulus clouds form during the day when the sun heats the ground, causing air to rise in columns called thermals. These clouds are usually scattered across the sky with breaks of clear blue sky visible between them.
Formation & Characteristics
How They Form
- 1. Solar Heating: The sun heats the ground during the day, warming the air above it.
- 2. Thermal Lift: Warm air rises in columns called thermals, carrying moisture upward.
- 3. Cooling & Condensation: As air rises and cools, water vapor condenses around particles, forming clouds.
- 4. Cloud Top: When the rising air can no longer rise (inversion layer), the cloud stops growing, creating a flat top.
Key Characteristics
- ✓ Shape: Puffy, lumpy appearance with rounded tops
- ✓ Base: Flat, well-defined base at same height
- ✓ Color: Brilliant white tops, slight gray shadow on base
- ✓ Vertical Growth: Often taller than they are wide
- ✓ Spacing: Individual clouds with clear sky between them
- ✓ Transparency: Can see sun shining through the clouds
Daily Development Pattern
Morning (6-9 AM)
Few cumulus clouds begin forming as sun heats the surface
Midday (10 AM-2 PM)
Peak development with scattered cumulus clouds across the sky
Afternoon (3-5 PM)
Some convective towers may grow, potentially forming showers
Evening (6+ PM)
Clouds dissipate as solar heating stops
Cumulus Variations
Cumulus Congestus (Towering Cumulus)
Larger cumulus clouds that have grown vertically due to stronger convection. Can reach 20,000+ feet and may develop into thunderstorms if conditions are right.
- • Much taller than wide
- • Can reach 3,000-5,000+ feet vertical extent
- • Often in rows or chains
- • May produce light showers
Cumulus Humilis (Fair Weather Cumulus)
The classic fair weather cumulus with minimal vertical development. These are the puffy clouds typically seen on pleasant days.
- • Relatively small in vertical extent
- • 500-1,500 feet tall
- • Widely scattered
- • No precipitation
What Cumulus Clouds Mean
☀️ Fair Weather Indicators
- ✓ Scattered individual clouds mean stable conditions
- ✓ Flat bases at consistent altitude indicate steady air flow
- ✓ No rapid growth signals no severe weather development
- ✓ Best weather typically occurs in morning/afternoon
⚠️ Warning Signs
- • Rapid vertical growth = thunderstorm potential
- • Increasing coverage = weather may change
- • Merging clouds = stronger convection developing
- • Dark bases = moisture-laden air, possible showers
Key Facts About Cumulus Clouds
Size & Scale
- • Typically 1,000-2,000 feet across
- • Base height: 3,000-5,000 feet
- • Vertical extent: 500-3,000 feet
- • Individual clouds easily identified
Seasonal Patterns
- • Most common in warm months
- • Peak in spring/summer afternoons
- • Less common in winter
- • Rare at night (no solar heating)
Composition
- • Water droplets (not ice)
- • Droplet size: 10-20 micrometers
- • Millions of droplets per cloud
- • Liquid water content: 0.3 g/m³
Visibility & Observing
- • Easily visible from ground
- • Can see sun through thin areas
- • Good for cloud spotting
- • Associated with good weather
How to Spot Cumulus Clouds
Look For:
- • Bright white, puffy appearance
- • Flat, well-defined base
- • Individual, separated clouds
- • Clear blue sky between clouds
- • Most visible midday
Best Viewing Times:
- • Warm, sunny days
- • Late morning to early afternoon
- • After clear, calm nights
- • When sun is higher in sky
- • Spring and summer months