Northern Mexico is projected to become more arid in the future, however the magnitude, timing and spatial extent of precipitation change is presently poorly constrained. To address this, we have developed a multi-proxy (δ18O, δ13C, Mg/Ca) U-Th dated speleothem record of past rainfall variability spanning 4.6 to 58.5 ka from Tamaulipas, Mexico. Our results demonstrate a dominant thermodynamic control on hydroclimate via changes in Atlantic SSTs. Our record robustly demonstrates this response during major paleoclimate events including the Last Glacial Maximum, the Younger Dryas and Heinrich Stadials 1, 3, 4, and 5. While previous work has suggested the magnitude of the Caribbean Low-Level Jet as the predominant driver of regional rainfall, we utilize a state-of-the-art climate model to isolate cool Atlantic SSTs as the dominant mechanism of drying. We also demonstrate this response is consistent across large parts of Mesoamerica, suggesting drying in the future may be more spatially homogenous than currently predicted.