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).…