Each model used negative binomial regression and used generalized additive models to estimate degrees of freedom for non-linear (i.e. spline) variables. Changes in AICc and relMAE compared all models to the reference (model 1), a seasonal variables-only model that contains calendar week, average weekly temperature, and average weekly relative humidity. Abbreviations: ∆AICc, change in Akaike’s Information Criterion corrected for small sample size; RH, relative humidity.