The purpose of this study was to determine the spatial and temporal aspects of the urban heat island in the small, arid city of Casa Grande, Arizona. Temperature and dewpoint were collected through a combination of fixed stations and two mobile transect routes on four separate clear and calm nights during the period of 15–18 March 2004. A mobile transect on 18 March revealed a maximum heat difference of 4.7°C along an east-to-west route across the city, with a spatially interpolated temperature map illustrating warmest areas in the far eastern commercial corridor and cooler areas in the far southern and western regions of the city, consisting of rural agricultural fields. Wind speed at the Casa Grande Airport during transect times was seen to be a significant factor in determining intensity of heat differences. However, due to very light wind conditions encountered on all three nights (<2.5 m s⁻¹), surface thermal properties and land cover may have played the largest role in determining heat island intensity. Thermal imagery taken of the area at a time similar to transect times (2125 LST) confirms the idea that surface thermal material properties may play a large role in determining heat island characteristics near the ground with the absence of strong winds.