Hail Size Chart

Wind Speed Estimate

Current Conditions

Reference Information 

What makes a thunderstorm severe?

A severe thunderstorm is a thunderstorm that produces...

• wind gusts of at least 58 mph (50 knots), and/or
• hail at least 1 inch diameter (quarter size) and/or
• a tornado

  Hail Size Chart: (diameter in inches) (visual chart)

• Pea Size: 0.25 inches
• Small Marble: 0.50 inches
• Penny: 0.75 inches 
• Nickel: 0.88 inches
• Quarter: 1.00 inches <--Any hail this size or larger is severe thunderstorm criteria
• Half Dollar: 1.25 inches
• Ping Pong Ball: 1.50
• Golf Ball: 1.75 inches
• Hen Egg: 2.00 inches
• Tennis Ball: 2.50 inches
• Baseball: 2.75 inches
• Grapefruit: 4.00 inches
• Softball: 4.50 inches

Wind Speed Estimate:

• 25-31 mph: Large branches in motion; whistling heard in telephone wires.
• 32-38 mph: Whole trees in motion; inconveniencefelt walking against the wind.
• 39-54 mph: Twigs break off trees; wind generally impedes progress.
• 55-72 mph: Damage to chimneys and TV antennas; pushes over shallow rooted trees.
• 73-112 mph: Peels surfaces off roofs; windows broken; light mobile homes pushed or overturned; moving cars pushed off road.
• 113-157 mph: Roofs torn off houses; cars lifted off ground.

Frequently Asked Questions about Spotter Training Sessions

1. Do I need to preregister for these sessions? No. All you need to do is arrive at the proper time and location.
   
   
2. About how long do the sessions last? Approximately 2 hours.
   
   
3. Do I have to live / be a spotter in the county that I take the training session? No. The training sessions are identical.
    
4. Is there online training I can review after attending the training course? Yes. You can find the online training at: http://www.crh.noaa.gov/ind/INDSpotter/player.html