The increasing frequency of extreme hot days has a considerable impact on health and energy. Heat stress related to high temperatures cause increased rates of mortality and morbidity, particularly amongst vulnerable populations such as those belonging to lower socio-economic groups. Most studies on heat related mortality and morbidity generally use temperatures from weather stations that do not consider the urban heat island (UHI) effect, leading to inaccurate predictions, particularly during heat waves. This study uses data collected by citizen scientists in predicting outdoor thermal comfort as well as indoor heat stress and peak cooling energy for low income housing in Australia. The results show that the outdoor Universal thermal climate index (UTCI) values estimated during hot afternoon ranged from 26 degrees C to 46 degrees C which equate to moderate to extreme heat stress. The indoor Discomfort index (DI) values calculated inside the living and bedrooms were below the heat stress limits (DI < 28) when Bureau of Meteorology (BoM) data was used as the input for calculation. However, indoor DI exceeded the threshold when actual on-ground data was used in the calculations, indicating that people will be at severe risks of heat related illnesses. It was also found that 60% of the time DI exceeded the threshold value as opposed to 2% with the use of BoM data. Furthermore, the peak cooling load was increased by 24% when on-ground data was used. The results show that low income houses and the neighbourhoods where they are located can cause significant heat related health risks which are normally overlooked in typical simulation studies. This study demonstrated a cost-effective way of collecting microclimate data for urban heat island mitigation and adaptation studies. (C) 2020 Published by Elsevier B.V.