The Golden Horseshoe is a densely populated area in southern Ontario and the population is expected to grow to 11.5 million residents by 2031. The urbanization process will likely intensify due to the current and expected population growth. The urban heat island (UHI) effect at 19 meteorological stations in southern Ontario were assessed using climate normals from 1981-2010 and the local climate zone (LCZ) method. The stations were assigned an LCZ unit based upon their calculated impervious, pervious and building surface fractions. It was found that areas representing higher urban-centric zones had higher UHI intensities (LCZ 5 with 2 K) than areas that were less urban-centric (LCZ 9 with 1.12 K and LCZ 6 with 1.37 K) revealing a continuum of “urbanicity”. The LCZ method provided greater objectivity when calculating the UHI intensity than the simpler method of an urban / rural dichotomy. With expected warming and population growth in the area the detrimental human health, environmental and economic impacts associated with the UHI effect should be given consideration for any future planning and decision making.