A climatology of the urban canopy layer heat island (UHI) of Vancouver, British Columbia, Canada is presented based on three years of hourly differences of air temperature between an urban and a rural site. Diurnal and seasonal variations in heat island magnitude and of rural cooling rates at the two sites are examined. The relationships between nocturnal maxima UHI and weather (wind speed, cloud amount and type) are also examined. Diurnal variability of UHI magnitude follows a simple pattern with minima occurring at approximately mid afternoon, and maxima midway between sunset and sunrise. Small seasonal variations in this pattern are evident. Nocturnal UHI magnitude decreases with increasing wind and cloudiness in agreement with previous findings in several cities. It was anticipated that seasonal variations in rural surface thermal admittance (controlled by soil moisture) would result in large seasonal variations in nocturnal UHI magnitude. However, observed seasonal differences in UHI magnitude were less than expected, while short-term variations were larger than expected. Given Vancouver’s coastal location, on-shore winds also influence UHI magnitude, depending on the sign and size of land-sea temperature differences and on the relative land fetch of the urban and rural sites. Summer negative UHI occur almost exclusively in westerly (on-shore) flow because the cooler marine air suppresses the urban maximum temperature.