Increasing incidence of extreme weather events has placed the management of heat stress at sporting events under the spotlight. Guidelines to manage and mitigate heat stress for those competing in and attending outdoor sporting events are increasingly important and pertinent. Our aim was to determine the guidelines currently available internationally. The secondary aims were to assess the specific advice for minimising heat stress and to determine the suitability of guidelines for both the specialist and wider populations. A search of government, sports medicine, and international sporting events organisations in the Anglosphere and host countries for previous and upcoming international sporting events (IOC, FIFA etc) and the six most popular outdoor sports club organisations in each Anglosphere country was conducted. Websites were systematically searched using the combined terms “weather”, “guidelines”, “physical activity” and variations of, for documents containing relevant advice. Advice was categorised into 13 components, including strategies to prevent or treat heat stress, assessing environmental parameters and scientific rationale. The occurrence of recommendations for each category was quantified using NVivo 12 software. Websites of 198 organisations in 37 countries were searched. No guideline documents were found for 74% of the websites; 133 documents were retrieved from the remaining 26%. 87% of the 133 guidelines, listed strategies to prevent heat stress and 32% gave strategies for treatment of heat stress. Only 29% of guidelines referred to environmental conditions, such as which environmental parameters should be assessed and how, and/or the use of a thermal index. Of those guidelines highlighting environmental conditions, 74% provided advice specific to certain conditions e.g., stated cut-off temperature at which play should be suspended. References were provided on 22% of guidelines, mostly referring to primary scientific literature. At present, the available guidelines are often poor and provide limited clear and consistent advice for protecting those involved in sport and physical activity in extreme heat events. Guidelines are inconsistent in the advice they give within the categories of preventing heat stress and assessing environmental conditions. Guidelines give greater emphasis on preventing heat stress over detailing practical methods for treating it. Measurement and interpretation of local environmental conditions is often not given. The use of environmental indices as a tool for determining cut off criteria for suspending or cancelling play is very limited. Guidelines lack strong supporting evidence and those that do cite scientific documents have often compromised the suitability of the guidelines for use by non-specialist populations. Improved evidence based guidance is clearly needed.