Straight-line winds are responsible for most thunderstorm wind damage. One type of straight line wind that can cause extreme damage is a downburst , a small area of rapidly descending air beneath a thunderstorm. Downbursts can reach speeds equal to that of a strong tornado and can be extremely dangerous to aviation. Large hail stones can fall at speeds faster than 100mph. The costliest US hailstorm occurred in Denver, CO in July, 1990.
Lightning is perhaps the most spectacular phenomenon associated with thunderstorms.
Most lightning deaths and injuries occur when people are caught outdoors, most often in the summer months and during the afternoon and early evening. In the past decade, over 15,000 lightning-induced fires nationwide have resulted in several hundred million dollars a year in damage and the loss of 2 million acres of forest. Your chances of being struck by lightning are estimated to be 1 in 600,000 but could be reduced by following safety rules. When conditions are favorable for severe weather to develop, a severe thunderstorm watch is issued. When severe weather has been reported by spotters or indicated by radar, a severe thunderstorm warning is issued.