•Olive transpiration measured in a sub-humid climate exhibited similar seasonal patterns as those reported for a Mediterranean climate.•The basal crop coefficients measured in a temperate sub-humid climate were of similar magnitude as those reported for arid and semi-arid climates.•The linear model developed between the Kcb and canopy light interception based on two years data explained 66% of the variation in the Kcb. Young non-bearing olive trees were grown in drainage lysimeters and their water consumption was measured over two consecutive yearly-experimental periods to analyze the effect ofseasonal variations on the basal crop coefficient (Kcb). Micro-lysimeter measurements were used to quantify soil evaporation (Es) and Es was subtracted from evapotranspiration (ETc) to determine transpiration. Monthly mean (Kcb) were determined as (ETc-Es)/ETo, where ETo is the FAO-PM grass-reference evapotranspiration, calculated from locally measured weather data. The observed Kcb value at mid-season, 0.38, was obtained in the fall months, with 41% of canopy cover. The mid-season Kcb when adjusted to the FAO-56 standard climate was 0.43. Seasonal patterns of Kcb are presented and the Kcb value during the mid-season growth-stage was found to be similar to those described in the literature for Mediterranean climates. Variation of the basal crop coefficient was satisfactorily explained by measured canopy light interception (FIR) and a linear regression model is presented for Kcb as a function of FIR.