Vegetation uses loses water through stomata in exchange for gaining carbon, and the rate at which this exchange is made is known as water use efficiency (WUE). WUE is an important parameter for monitoring the connection between the carbon and water cycles, and it can vary across vegetation types and water availability. However, the range of WUE variability with drought conditions has remained understudied in comparing how different ecosystems will respond to drying conditions. Future changes in climate are likely to lead to more extreme wet and dry conditions, with potential implications for vegetation’s ability to utilize water effectively. Here, we use a cross-network collection of eddy covariance sites (e.g., from FLUXNET2015, ONEFlux, ICOS, AmeriFlux FLUXNET) to evaluate WUE sensitivity to drought. We use the Palmer Drought Severity Index (PDSI) from TerraClimate to quantify drought conditions. Initial results at the monthly scale suggest that both humid and arid climates downregulate maximum WUE by a similar relative amount during drought conditions (PDSI < 0) compared to non-drought conditions (PDSI > 0). For example, the 95^th percentile at US-MMS, in a humid climate in Indiana, during drought is 87.5% (0.0041 g C / ml) of the 95^th percentile during non-drought (0.0046 g C / ml); at US-Wkg, in an arid climate in Arizona, 0.0014 g C / ml during drought is 87% of 0.0016 g C / ml during non-drought. Further analysis will investigate how consistently this holds across the network and across gradients of aridity.