Rising temperatures under climate change threaten athlete safety at the Summer Olympics due to increasing heat stress likelihoods. For outdoor sports, suspending activity (i.e. rescheduling or cancelling) is the only possible intervention for mitigating heat stress risk in excessively hot or humid conditions, presenting logistical challenges to organizers. We evaluate the event suspension probability of outdoor Summer Olympic sports in past and potential future host cities due to unsafe climatic conditions for the recent past (1983–2016) and future projected in 2050. Assuming that >50% event suspension probability is logistically prohibitive, the number of viable host cities decreases from 709 to 595 (16%) in 2050. Remaining viable hosts are more affluent, located at higher elevations and latitudes, or in the Southern Hemisphere. Our results highlight growing heat-related risks at athletic events and can inform planning and adaptation priorities for future Summer Olympics.