The following tests were performed: 1) smoothed temperature, dew point, and air mass frequency, lagged 17-days, between mortality events (z$1) and nonevents (z,1) using an unpaired two-sample t-test ( Figure S3 ); 2) same as in 1 for unsmoothed temperature and dew point temperature (to determine if a strict 17-day lag exists); and 3) same as in 1 but using a one-sample t-test (to account for the possible influence of disparate sample sizes between groups).