Forty-two years of lightning casualty and damage reports in Colorado are summarized. The data are from NOAA's Storm Data, which is compiled monthly by the National Weather Service.

The dataset contains 103 deaths, 299 injuries, and 191 damage reports from 1950 through 1991. Time fluctuations of these lightning events are shown by classifying the data by year, month, and hour of the day. Additional information is provided on age and gender of lightning victims.

Houses were the most common objects reported as damaged by lightning. Fire was the most common source of lightning damage to structures or objects. Comparisons are made of these and other results, when possible, with previous studies of lightning in other locations around the world.

Geographical patterns of lightning incidents for the state are shown in maps of total number of casualties, and number of casualties normalized by population density for each county. Much higher casualty rates per population and area occur over the mountains and some areas of the eastern slopes than elsewhere.

Most often, people were involved in recreation or employment when they became lightning victims. Most frequent locations of lightning casualties, in order, were summits of mountains and ridges, under trees, in the open, and at lakes. Outdoor recreation casualties were most frequent in the mountains, agricultural cases over the eastern plains, and sports and domestic casualties along the urban corridor east of the mountains.

Year-to-year variability was high in all categories. When compared to the steady increase in the population of Colorado, there were fewer casualty and damage reports during the 1970s and early 1980s than before and after that period. Ranch and farm casualties decreased greatly after the early 1960s. Outdoor recreation, urban, and work cases steadily increased over the entire period in accordance with the population increase. However, sports casualties increased at a substantially larger rate than would be expected from the population increase. Statewide lightning victim counts by 5-year periods correlate well with statewide summertime temperature, but not as well with precipitation.

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