The spatial variability of the urban air temperature for the city of Hamburg is analyzed based upon a one-year dataset of meteorological and pedological measurements. As local air temperature anomalies are subject to land-use and surface cover, they are monitored by a network of measurement stations within three different urban structures. Mean annual temperature deviations are found to be +1.0K for inner city sites and +0.25 K to -0.2K for suburban sites compared to a rural reference. The nocturnal urban heat island (UHI) is identified and averages +1.7K at the inner city stations, +0.7K at a suburban district housing area and +0.3K at a nearby green space. The observed UHI effect is most prominent when the wind speed is low (≤ 2ms-1) and the sky is only partly cloudy (≤ 6/8th). In spring 2011 an average inner city UHI of up to +5.2 K is observed during situations matching these conditions, while the extraordinary dry fall of 2011 lead to remarkably high air temperature differences at all observed stations. As expected, no evidence for a significant impact of topsoil moisture on nighttime UHI effect is found. The analysis of air temperature anomalies during daytime results in an annual mean deviation of -0.5 K above unsealed, vegetated surfaces from a sealed site during days with a turbulent mixing induced by wind speed > 2ms-1. Here, there is an indication for a relation between the water content of upper soil layers and the warming of air: 11 to 17 % of the variance of the diurnal air temperature span is found to be explained by the soil water content for selected relevant days.