National Oceanic and Atmospheric Administration (NOAA)/National Centers for Environmental Information (NCEI)
The nClimGrid-monthly dataset is a gridded dataset derived from spatially interpolating data from the Global Historical Climatology Network (GHCN). The dataset includes monthly precipitation, monthly temperature average, monthly temperature maximum and monthly temperature minimum. The dataset provides monthly values in a approximate 5x5 km lat/lon grid for the Continental United States. Data is available from 1895 to the present. On an annual basis, approximately one year of "final" nClimGrid will be submitted to replace the initially supplied "preliminary" data for the same time period. Users should be sure to ascertain which level of data is required for their research.
The quality control and spatial interpolation methodology is described in the publication 'Improved Historical Temperature and Precipitation Time Series for U.S. Climate Divisions'