Warmer temperatures associated with climate change have affected the phenology of most plants, but limited information exists for the American cranberry (Vaccinium macrocarpon Ait.). We examined long-term spatiotemporal trends in cranberry bud development during spring using detailed field observations of cranberry bud stages over a 65-yr period, spanning from 1958–2022. A growing degree day (GDD) model was further used to interpret the observed trends in bud development over the study period. To assess spatial variability in cranberry bud development, the GDDs were computed using gridded weather data for four counties of Massachusetts, representing 85% of the state’s cranberry acreage. A Theil-Sen linear regression model was implemented to determine trends in the occurrence of the cabbage head stage. We found significant temporal trends (p-value < 0.01) in the annual timing of white bud and cabbage head stages using the field observations, which were occurring 18 to 20 days earlier than was observed 65 years ago in the spring. GDDs accumulated at a faster rate in spring towards the end of the study period due to rising mean air temperature. Analysis of 65 years of gridded data revealed a significant trend (p-value < 0.01) of earlier phenological development across the four counties. The rate of advancement in cabbage head stage ranged from -0.15 to -0.25 d yr -1 across the study area. These findings highlight the need to update frost forecasting models that account for changes in growth schedule of cranberry.