In addition to heavy rains and the threat of lightning, hail can pose a big danger during a thunderstorm. Hail can be as small as the size of a pea, or as large as a softball. Because it falls from the sky, it can reach extremely high speeds as it barrels toward earth and damage anything in its path ”“ cars, windows and especially plants and agricultural crops.

If you see or hear hail hitting the ground during a thunderstorm, take it as an unmistakable sign that you need to remain inside if you're already indoors, or find shelter quickly if you're outdoors. A few facts about hail:

• Though hail rarely causes fatalities, more than 20 people are injured by falling hail each year in the United States.
• Hail size is measured by National Weather Service Doppler radar, which estimates the size of hail according to its diameter. Sizes range from pea-size (1/4 inch), to quarter size (1 inch) and golf-ball size (1 3/4 inches), all the way up to softball-size (4 1/2 inches). Hail larger than quarter-size (1 inch in diameter) is considered severe.
• The larger the thunderstorm, the greater the chance for larger hail to be produced ”“ so stay alert if you notice especially large thunderstorm clouds developing in your area.
• The majority of hail damage each year occurs to agricultural crops, as the area of the U.S. most at risk for large hail lies in the western Great Plains states. This 625-square-mile-wide area sees an average of 7 to 9 days with hail each year.