The National Heat Wave Plan draws on epidemiological knowledge to identify vulnerable populations and define appropriate preventive measures to reduce the impact of heat waves. This article presents a review of heat-related risk factors to determine whether new factors have emerged and whether certain populations should be given greater consideration. This literature review builds on an initial synthesis conducted in 2003 and on 39 relevant articles identified through a PubMed search. It highlights risk factors influencing heat exposure (lack of vegetation, urban heat islands, pollution, humidity, heat-exposed occupations, etc.), individual susceptibility (age, pre-existing conditions: cardiac, neurological, respiratory, endocrine, use of certain medications), and adaptive capacity (poverty, isolation, risky behaviors). Three studies point to risks associated with pregnancy (congenital malformations or prematurity) that were previously little known. Most of the identified risk factors were already known and are taken into account in prevention plans targeting specific populations such as the elderly, workers, and athletes, for example. Risks related to pregnancy warrant tailored prevention measures, especially since certain simple measures can be implemented. Furthermore, urban factors (vegetation, urban density, building quality) justify the implementation of long-term adaptation policies combined with ad hoc measures (urban irrigation).