A new framework for understanding the macro-scale variations in spring phenology is developed by using new data from the USA National Phenology Network. Changes in spring budburst for the United States are predicted by using Coupled Model Intercomparison Project phase 5 outputs. Macro-scale budburst simulations for the coming century indicate that projected warming leads to earlier budburst by up to 17 days. The latitudinal gradient of budburst becomes less pronounced due to spatially varying sensitivity of budburst to climate change, even in the most conservative emissions scenarios. Currently existing interspecies differences in budburst date are predicted to become smaller, indicating the potential for secondary impacts at the ecosystem level. We expect that these climate-driven changes in phenology will have large effects on the carbon budget of U.S. forests and these controls should be included in dynamic global vegetation models.