Progress of spring, is evidenced in the climate record. In deci- duous forests, leaf emergence provokes an abrupt change in Bowen ratio. Observations for several years at Harvard Forest, in north central Massachusetts have shown that the directly-measured Bowen ratio drops from >4 to <0.5 in the course of 5-10 days. Such rapid changes in energy partition should provoke changes in the surface layer conditions. Schwartz and colleagues have iden- tified the onset of spring from a lilac phenology network and then investigated the climatic response. In this work, we have be detected the onset of spring using the climatic data alone, unconstrained by separate plant phenology data. For 80 first- order stations for which temperature and humidity are available along the east coast of the US, we compiled the daily maximum temperature (Tm) and q for 30 year averaged data. An ersatz Bowen ratio B' was constructed by assuming that surface fluxes of heat and water vapor converge into a mixed layer: B' = [Cp/L][dTm/dt]/[dq/dt] . The progress of spring is identified by finding the day of the year for which B' first falls below 1. We find that the onset of spring obtained in this fashion fits well with the 'green-up' seen in satellite based vegetation index observations. Indeed, Hopkin's Law, from 1918, a purely geo- graphical rule, is a good baseline for this process. To refine spatial representativeness, we have performed a similar analysis using 800 climate stations from Georgia to Maine, for which Tmax and Tmin are available. Animations will be presented to illus- trate how the 'velocity of spring' varies with topography and proximity to the coast. These demonstrate that maximum tempera- tures move eastward from NY into New England with spring, even as 'spring', as determined by the B' criterion moves inland from the coast. A subset of stations for which data are available for more than a century are used to assess the hypothesis that the intensity of the Bowen ratio change with spring has been altered by the widespread reforestation of the eastern U.S.