The damaging effects of climate change and increased ocean temperatures are already visible in marine ecosystems worldwide. Degree heating weeks (DHW) provide a valuable metric for gauging excess sea surface temperature warming and coral bleaching risk. This study produces future DHW projections for the Mesoamerican reef (MAR) using a multi-model climate change ensemble. We show that current marine heat wave conditions linked to coral bleaching will be far exceeded in an average year by mid-century, creating an environment where MAR corals have no opportunity for normal year recovery between extreme years. The dramatic increase in DHW in the MAR indicates strong adaptation interventions need to be developed and implemented as soon as possible to support local communities in adjusting to the effects of a warming climate.