Hurricanes are among the most destructive weather systems in the global tropics and subtropics with the capacity to impact millions of people annually worldwide. Several different aspects of hurricanes that are relevant to impacts upon landfall have been studied, such as intensity, frequency, translation speed, etc. However, how the storm size itself may have changed over time has hitherto received less attention, partly because of the lack of reliable long-term observations. Here, we address this using a novel combination of observations and reanalysis. First, we show that using the radius of 8 ms^-1 (R8) winds as a metric for hurricane outer size, we are able to reasonably capture spatial trends in storm size over the period 2002-2022. Next, we extend the record backwards in time using R8 from reanalysis as a proxy and show that over the period 1979-2022, there has been a significant increase in hurricane outer size over the North Atlantic, especially over the western subtropics near the US coast. Analysis of the largescale environment indicates that these trends are consistent with an increasingly thermodynamically unstable atmosphere over that region. Further, we are able to demonstrate that these increases in storm size have substantial implications for coastal and inland flooding. Examining a suite of E3SM simulations reveals that the model is able to broadly reproduce the trends in storm size and environment in the western North Atlantic, supporting the observed trends. Finally, analysis of CMIP6 simulations indicates that the changes in the environment are likely driven by climate change and that they may continue into the future.