The combination of climate change, Urban Heat Island, and heatwave events is leading to higher daytime temperatures and causes elevated heat stress for urban dwellers. This magnified heat stress increases heat-related morbidity and mortality levels, mostly in vulnerable sectors of society, especially when correlated with poor air quality levels. This paper investigates the impact of high-to-extreme heat events and poor air quality on community health responses (mortalities and emergency department visits). It searches for correlations among meteorological parameters (air temperature and relative humidity), air quality (ground-level ozone and particulate matters concentrations), and the health response measured by the daily records of emergency visits and mortalities. A novel multi-dimensional clustering approach was proposed by combining hierarchical and k-means clustering to promote flexibility and robustness to improve the correlation procedure. The study focused on the health records of the elderly population with respiratory-cardiovascular diseases. The developed method was tested by investigating the instant impact of ambient air temperature, relative humidity, ground-level ozone, and fine particulate matter on the health records during hot and warm seasons in municipalities of Mississauga and Brampton, Peel Region, ON, CA for 15 years. The analysis confirmed the association between extreme heat conditions and poor air quality levels and mortalities and emergency visits of elderly people with respiratory-cardiovascular diseases.