Global warming due to increasing greenhouse gases is responsible for some of the overall heating observed in Los Angeles and the rest of California. Most of the increase in heat days and length of heat waves, however, is due to a phenomenon called the "urban heat island effect." Read more here.
I live on acreage with many trees. My car registers outside temperature. 6 kilometres away is our local shopping centre - Westfield Tuggerah. There can be 10ºC difference etween my house and the Tuggerah Heat Island