Association of daily high temperatures with increased snake envenomations: A case-crossover study

The prevention of snake envenomations in North America often focuses on avoiding interactions between humans and snakes. Previous strategies have focused on the influence of geography, type of habitat, and time of year, though a detailed analysis of weather patterns on snakebite envenomation behavior is lacking. We present a case-crossover study of non-pregnant adults (n = 489) who reported snake envenomations to a single state's poison control center from 2014 to 2018. Age and gender of the individual, as well as the date, time, zip code associated with the envenomation, and snake descriptions were collected. Information regarding barometric pressure, actual temperature, high and low daily temperature, and weather condition (fair, cloudy, or rain/precipitation) was collected and compared to the same zip code, date, and time exactly one week and one year prior to the envenomation using historical data from the Weather Underground database. Paired t-tests and Stuart-Maxwell tests were used to determine differences in weather conditions during the study period. This study was IRB-approved. At the time of envenomation, the weather was most often fair (52.2%), followed by cloudy (44%), and least frequently demonstrated rain/precipitation (3.9%). Snake envenomations increased significantly (p < 0.0001) on days with an elevated daily high temperature. There were statistical differences in the distribution of weather conditions (fair, cloudy, or rain/precipitation) on the day of envenomation compared to one week prior (p < 0.0001) and one year prior (p < 0.0008). Comparisons based on both control groups indicated that envenomations were significantly less likely to occur during rain/precipitation and cloudy weather than during fair weather. Limitations include its retrospective nature and low total number of envenomations. In our single-center study, snake envenomation behavior as it relates to readily reportable weather measurements, appears to be associated with the warmer days, the overall high temperature on the day of envenomation, and fair weather conditions. Actual temperature at the time of envenomation, low temperature, barometric pressure, and precipitation at the time of envenomation do not appear to be associated with an increased risk of envenomation. Additional studies to determine the cause of these associations would be beneficial in further delineating the findings of this study.