Lake evaporation is a dominant yet poorly constrained component of water and energy budgets. This uncertainty critically undermines necessary paleoclimate reconstructions, particularly for terminal lakes, whose levels are considered the best direct indicators of the precise balance between catchment precipitation and evaporative losses. Thus, a better estimation of the evaporation can help in determining modern and past hydrological cycles. Here, we address this challenge by applying a robust, physically grounded framework for lake evaporation, based on direct measurements and theoretical analysis of lake energy-balance and its thermal equilibrium solution, combined with calibrated bulk formulae. Our direct high-resolution data are based on long-term eddy-covariance measurements from three adjacent lakes in the Dead Sea rift, together with published data from a nearby semi-enclosed sea. These lakes, with similar incoming radiation, span wide gradients in salinity (freshwater to hypersaline), climate (Mediterranean to hyper-arid), depths, and thermal stratification. We present simple, yet accurate, bulk formulae that relates the environmental conditions to evaporation and heat fluxes. The applied approach of lakes’ thermal equilibrium depends on their thermal response time; shallow lakes reach equilibrium or are very near equilibrium at intra-annual timescales, whereas deeper stratified lakes reach thermal equilibrium only under annual forcing. This equilibrium-based framework and calibrated bulk expressions, therefore, provide the tools for modeling lake evaporation globally using only environmental data, and for reconstructing paleo-evaporation from environmental proxies. Applying this framework to the Last Glacial Maximum (LGM) highstand of Lake Lisan, in the Levant, this method bounds the values of evaporation rates, which, in turn implies a minimum of approximately four times larger last glacial annual water inflow than modern inflow; these values are needed to stabilize the lake and to balance the annual evaporation. In turn, they indicate much larger precipitation in the Dead Sea watershed during the LGM.