This data set is associated with the study "DDRP: real-time phenology and climatic suitability modeling of invasive insects" by Barker et al. (2020). We temporally downscaled monthly PRISM estimates for 1961‒1990 because DDRP requires daily data and PRISM daily temperature data for years prior to 1980 are not available. For each month of a given year, a bilinear interpolation method was used to assign each day an average temperature value that was iteratively smoothed and then adjusted so that the monthly averages were correct. Code for this analysis was written partially in Perl and partially in Octave, and is available at https://github.com/bbarker505/dailynorms. We temporally downscaled monthly PRISM estimates for 1961‒1990 because DDRP requires daily data and PRISM daily temperature data for years prior to 1980 are not available. For each month of a given year, a bilinear interpolation method was used to assign each day an average temperature value that was iteratively smoothed and then adjusted so that the monthly averages were correct. Code for this analysis was written partially in Perl and partially in Octave, and is available at https://github.com/bbarker505/dailynorms and https://doi.org/10.5281/zenodo.3601671.