Previous studies of the influences of land use/land cover changes (LULCC) on the climate of continental areas have provided a basis for our current understanding of LULCC impacts. However, continental climates may not provide complete explanations or answer specific scientific questions for other regions, such as small tropical-maritime dominated islands. Here we present a detailed analysis of temperature change over the past century for the tropical island of Puerto Rico, using an approach that accounts for internal climate variability and spatial resolution issues and assesses the degree to which some of this change might be related to urban development. Long-term weather data, digital maps, geographic information systems (GIS) and statistical analysis were used to detect and assess differences between urban and non-urban temperature records. Strong evidence of a relationship linking temperature magnitudes to local urban development was detected, and the analysis suggests that urbanization has increased minimum, maximum and average temperatures by 0.5 °C in the warmest regions to 2 °C in the coolest regions. The results also show that the magnitude of temperature impacts depends on the contextual ecology or environment where the development has occurred. Temperature differences between urban and non-urban areas are higher in colder and wetter microclimates than in dryer warmer ones, and were less pronounced for minimum temperature than for maximum temperature. However, because the levels of impacts are based on data that had some prior adjustment intended to control for urban signals, they represent minimum estimates of the impacts of land use on temperature in Puerto Rico.