Past riparian microclimate studies have measured changes horizontally from streams, but not vertically through the forest canopy. We recorded temperature and relative humidity for a year along a two-dimensional grid of 24 data-loggers arrayed up to 40 m height in four trees 2 – 30 m slope distance from a perennial second order stream in the Sierra Nevada. Our objective was to quantify diurnal and seasonal changes in vertical and horizontal microclimate gradients. Our data suggest a dynamic zone of riparian influence on microclimate that fluctuates diurnally and seasonally. Stream influence on microclimate was limited (statistically significant < 5.0 m vertically, < 7.5 m horizontally). In summer and winter, mean daily temperature and vapor pressure deficit (VPD) increased horizontally and vertically from the stream. Maximum absolute differences in temperature and VPD between upland and streamside conditions were greater in summer than winter. Winter diurnal ranges of temperature and VPD were dampened near the stream, increasing with distance, while summer diurnal ranges were greater near the stream and decreased with distance. Microclimate change was markedly greater vertically above the stream than horizontally. Such steep gradients of air temperature and moisture through the vertical forest profile likely affect arboreal habitat conditions that influence epiphytes and their animal communities.