Back in 2010 my team published this paper which includes a comparison of the health impact from heatwaves measured using:
Wilson, L. A., Morgan, G., Hanigan, I. C., Johnston, F., Abu-Rayya, H., Broome, R., Gaskin, C., and Jalaludin, B. (2013). The impact of heat on mortality and morbidity in the Greater Metropolitan Sydney Region: a case crossover analysis. Environmental Health : A Global Access Science Source, 12(1), 98. https://dx.doi.org/10.1186/1476-069X-12-98