Urban and regional temperature trends in southern Nevada, including the rapidly growing Las Vegas metropolitan area, were analyzed over two periods, 1940–2009 and 1977–2009. The data show that minimum temperatures in Las Vegas increased by more than 4°C above the regional trend since 1940 and by approximately 3°C more than the regional average since 1977, which demonstrates that urbanization has significantly altered the nighttime climate of the city and that the changes were most pronounced in the last 30 years. In contrast, regional minimum temperature increases were not widespread and generally limited to spring and summer with a regional annual average minimum temperature increase of about 1°C since 1940 and 0.6°C since 1977. Notably, there is little evidence of winter temperature moderation throughout rural southern Nevada in either time period investigated. The analysis also suggests maximum temperature trends in Las Vegas have been moderated by urbanization, as daytime temperatures across southern Nevada increased by approximately 1°C in the last 30 years, but no increase was observed within the city suggesting that Las Vegas has developed a moderate daytime urban cool island. While no absolute change in Las Vegas dewpoint temperatures was found, a relative increase of up to 3°C was observed when the city was compared to a rural control station. The relative increase in urban dewpoint temperature is significantly correlated to the daytime urban cooling trend, minimum temperature increase, and the significant reduction in diurnal temperature range, suggesting that increased latent heat flux in Las Vegas may be a primary cause of observed urban climate changes.