This paper explores how disaster risk knowledge shapes local heat wave risk management in London, UK. Its focus is on the implementation of the UK National Heatwave Plan through public sector organizations in London. Empirical evidence stems from 49 semi‐structured, expert interviews with risk managers from local authorities, and health and social care organizations in London. Findings suggest that the National Heatwave Plan is an important source of disaster risk knowledge, but that it has not been successful in steering sustainable change in the way that heat risk is planned for at the local level. The plan is perceived locally as a public health strategy focused on emergency response. This reinforces local heat wave planning approaches that are enacted through public health and that prioritize short‐term response actions, rather than long‐term preventive strategies. This paper argues that the provision of disaster risk knowledge can undermine paradigm shifts in local risk planning if it constrains consideration of alternatives to existing risk management approaches.