Reliable future climate projections and water deficiency assessments require precipitation observations that are both spatially comprehensive and temporally complete, yet many global regions still suffer from observation sparsity1,2. Here we evaluate the distribution of 221,483 internationally exchanged precipitation gauges worldwide, with records across 1900–2022, and further explore where new gauges are most needed under different scenarios. We find that at present only 13.4% of the global land surface meets the World Meteorological Organization requirements for annual precipitation monitoring, indicating widespread scarcity that has serious socioeconomic implications. Europe has the highest continental gauge density (2.4 gauges per 1,000 km2), with Germany leading among countries over 50,000 km2 (22.4 gauges per 1,000 km2). Globally, 25% of land surface already requires urgent expansion of gauge networks because of climate variability, including northern South America, northern North America, Central Africa and southern Asia. Considering projected precipitation changes and socioeconomic conditions under a high-emission scenario further identifies high-need regions in India, Greenland, Bolivia and China because of climate sensitivity and socioeconomic vulnerabilities, increasing this share to 32.1% of global land. Our findings highlight important gaps in global precipitation monitoring that require strategic investments in new gauges and underscore the need for open data access.
