Mean daily incident solar radiation of each month, for the Australian continent between 1970-2016. Monthly solar radiation regulates rates of plant growth. Modelled by expressing observed monthly solar radiation as normalised anomalies with respect to a standard Angstrom equation that expresses monthly solar radiation in terms of astonomically determined parameters and relative sunshine duration, as described in Hutchinson et al. (1984). The monthly anomalies were interpolated by trivariate thin plate smoothing spline functions of longitude, latitude and the proportion of wet days in the month using ANUSPLIN Version 4.5. This anomaly method provided a more direct, and more statistically robust, representation of the impact of precipitation on solar radiation than the method described in Hutchinson et al. (1984). The proportion of wet days, as provided by ANUClimate_v1-0_rainfall-proportion-greater-than-threshold_monthly_0-01deg_1970-2016, acted as simple surrogate for relative sunshine duration. There were on average 645 observed solar radiation totals for each month between 1970 and 1996 at 64 stations across Australia obtained from the Bureau of Meteorology. Automated quality assessment rejected on average 9 data values per month with extreme studentised residuals. The root mean square of all individual cross validation residuals provided by the spline analysis is 1.15 MJ m-2 day-1 (6% of the mean). A comprehensive assessment of the analysis and the factors contributing to the quality of the final interpolated monthly solar radiation grids is in preparation.