Cities are almost always hotter than the surrounding rural area but global warming takes that heat and makes it worse.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/urban-heat-islands-cooking-us-cities-report-shows
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/huffington-post-0
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/climate-change
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/climate-impacts
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/united-states-america-us
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/global-warming
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health-effects
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/energy