Sun and Rain: The World's Sunshine Against Its Rainfall. A Bivariate Reading of the CRU CL 2.0 Climatology, 1961 to 1990

Sunshine and rain are the two things most people mean by the weather, but they are usually mapped one at a time. I combine them in a bivariate map of the world's land, using the CRU CL 2.0 climatology for 1961 to 1990 on a 10 arc-minute grid: 566,262 cells with both mean monthly sunshine, which I convert from a percentage of possible sunshine to hours using the astronomical day length, and mean monthly precipitation. Classed by terciles of land area, the two measures are far from independent (Spearman's rho = -0.24). The sunny and dry corner holds 21.0% of the land and the sunny and wet corner only 3.0%, against the 11.1% expected if they were unrelated. The dull and dry corner, 7.3% of the land, is mostly subarctic, but among 573 cities of a million people or more it contains only Lima, Callao and Trujillo on the desert coast of Peru. The United Kingdom sits at the dull end of the world: its sunniest cell gets 1,774 hours a year, and 84% of the world's land gets more; only three of 156 countries are duller on average. A comparison with WorldClim 2.1 precipitation shows close agreement for rain (Pearson's r = 0.977), but no independent check is available for sunshine, which rests on far fewer stations. An interactive version lets readers re-cut the classes by month and by break, search 34,167 places, and find each place's closest weather twins. Interactive version: https://tristan-hotham.github.io/sun-and-rain/. Data and code: https://github.com/Tristan-Hotham/sun-and-rain. Blog post: https://blog.tristanhotham.com/2026/10/28/sun-and-rain/. Text, figures and derived data: CC BY 4.0; code: MIT. Climate data: CRU CL 2.0, Climatic Research Unit, University of East Anglia, New et al. (2002), shared as derived products with citation. Places: GeoNames (CC BY 4.0). Country outlines: Natural Earth (public domain). WorldClim 2.1 is used for summary statistics only and is not redistributed.