Terrestrial water availability is a key determinant of human and ecosystem well-being. Apart from mean precipitation and evaporation changes, it is unknown how daily-scale precipitation concentration into fewer, heavier events impacts hydrologic partitioning and the land water balance. Using satellite-derived terrestrial water storage estimates (TWS) and multiple observational precipitation datasets, we provide the first observational evidence that more concentrated precipitation decreases land water availability as strongly as total precipitation enhances it across all climates globally. Simple and complex land-surface models recover the observed effect and idealized simulations reveal that it arises from enhanced evaporation from hydrologic partitioning changes at the land surface. Projected TWS impacts of warming-driven rainfall concentration at ~2°C of warming shift the land surface to abnormally dry conditions (≥1/2 standard deviation) for 27% of the global population, independent of any total precipitation changes. Our results reveal new key determinants of the land water balance, highlighting its sensitivity to the temporal distribution of precipitation, with implications for water availability.