Aim A major heatwave occurred in Australia in early 2009 with considerable and varied health impacts in South Australia (SA) and Victoria. The aim of this study was to investigate the heat‐adaptive behaviours of older people in these states. Methods A computer‐assisted telephone survey of 1000 residents of SA and Victoria aged 65 years or older was conducted at the end of summer 2010–2011. Results The majority of respondents reported undertaking heat‐adaptive behaviours. In SA, there was a significantly higher proportion of households with air conditioning compared to Victoria, and a higher recall of heat‐health messages. In both states, self‐reported morbidity during heatwaves was higher in women, persons with poorer health and those with cardiovascular conditions. Conclusion An increase in global temperatures in conjunction with an ageing population is a concern for public health. Our findings suggest acclimatisation to hot weather may influence behaviours and health outcomes in older people.