Both hot and cold daily temperatures are associated with more workers’ compensation claims than days with mild temperatures, with up to 10% higher claim frequency, according to a report by the National Council on Compensation Insurance (NCCI). Temperature, the report continues, can be especially impactful for certain injuries and jobs. For instance, “Frequency effects of hot days are largest in outdoor sectors, especially construction; Cold and wet days have many more slip-and-fall injuries, as well as motor vehicle accidents.”
Prior studies merely focus on how heat impacts injuries and workers’ compensation claims by using heat data from Texas, California, a collection of U.S. states, or Australia, while getting inconclusive results from or excluding cold weather altogether. The NCCI report “expands on prior analyses by studying impacts of cold and precipitation as well as heat.”
Daily High Temperature Impacts
The study found that weather may impact the frequency of workers’ comp claims in a variety of contexts. “We find that injury frequency increases modestly but consistently with daily high temperatures all the way from about 50 degrees to 100 or more degrees Fahrenheit, with approximately a 1% increase in injuries for every five degrees of temperature,” states the report. “All else equal, there are also more injury claims on days with high temperatures around freezing. Frequency is lowest on the coldest days and days between 40-60 [degrees Fahrenheit].”
Precipitation Impact
“We find that precipitation leads to particularly high claim frequency on freezing days but lessens the frequency increase on warm or hot days,” according to the report. “On wet days when the high temperature is between 25 and 40 [degrees Fahrenheit], there are 7% to 10% more injuries than the baseline of 60-65 [degrees Fahrenheit] dry days, holding all else equal. On dry days at the same temperature, the same comparison is only about 1% to 3%. In short, workers’ compensation claims rise much more on days that are cold and wet than on days that are cold and dry.”
Overall, for both dry and wet days, frequency rises as daily high temperature increases, the report states. However, researchers estimate slightly larger effects on dry days and about one percent fewer injuries on a wet day than a dry day. “For the hottest days in our sample, we estimate a 10% increase in injuries on dry days compared to baseline, but only about 7.5% compared to baseline on wet days.”
Claims by Sector
“Compared to the 60-65 [degrees Fahrenheit] baseline, heat is associated with more claims in every sector,” states the report. “These effects are largest for construction, natural resources, and upkeep and maintenance (which includes landscaping)—all outdoor sectors. Effects are smallest for office and health care class codes, which are mostly indoor jobs in climate-controlled environments.”
For cold days, however, effects are largest in transportation and warehousing. In bad weather, and particularly wet weather, delivery drivers are affected by both road conditions and increased risk of slip and fall, the report states. “Office, health care, and upkeep also experience increased claim rates on cold days. For construction, natural resources, and manufacturing, injury frequency is lower on cold days than the mild-weather baseline. This may reflect that outdoor work is less likely to be performed on days with particularly harsh weather. In such a case, measured exposure would remain the same on such days, but workers would not be doing as much hazardous work.”
Cause of Injury
“For days warmer than the 60-65 [degrees Fahrenheit] baseline, claims increase with heat on dry days for all injury types,” the report states. “At the baseline temperature, there are more slip and falls and motor vehicle accidents on wet days than on dry days, but for the other injury types, there are more claims on dry days.”
Likewise, on cold days, frequency of injury is lower for contact, strain, and “all other” injuries than at the 60-65 degree baseline, according to the report. “The higher the overall frequency observed for 25-40 degree days is primarily due to large increase in slip and falls, and secondarily by an increase in motor vehicle accidents. Both claim types are especially prevalent on cold and wet days.” On cold and dry days, however, the impact on motor vehicle accidents is small, but frequency increases for slip and falls even on cold and dry days but is especially large on cold and wet days.
Throughout the 20-year study period, overall injury frequency has declined significantly for all types of workers, which may relate, “in part, to automation, safety technology, and loss prevention,” as well as a shift to remote work during the pandemic. However, researchers have found “only modest evidence that the relative risk on adverse weather days compared to our 60-65 [degree Fahrenheit] baseline has changed over time.”