During the third week of July 2011, Ohio experienced a heat wave with multiple heat advisories throughout its various cities. The total ED visits related to HRI peaked on July 21 (n0170, 107 males, 63 females), which was also the day with the highest maximum temperature (97.4 F). A time-series chart of these ED visits by age group is shown below. The data show that the most sensitive populations (ages 0-5 and 65 and older) were the least affected and likely were adhering to the heat advisories. The 18Á 39-and 40Á64-year-old age groups were most affected by the heat. Pearson correlation showed a strong relationship between HRI visits and mean temperature and dew point (r00.76 and r00.66), p B0.0001. Multiple linear regression analyses were completed to determine which weather variables were the best predictors with HRI. The best model showed that for every 1 unit increase in ED visits, there was a 3.88 unit increase in mean temperature, independent of mean humidity and wind speed, p B0.0001. The addition of mean dew point caused the model to have a high colinearity and was removed from the model.