Animated satellite-based map showing the build-up of ocean heat stress in the waters around Florida between June 25 and July 23, 2023. Coral reefs in the southern portion of the Florida Keys have been experiencing extreme heat stress for weeks. In areas where the Degree Heating Week (DHW), which is directly related to the timing and intensity of coral bleaching, reached 4 °C-weeks, significant coral bleaching is expected; in areas where the DHW reached 8 °C-weeks, severe coral bleaching and significant mortality are expected. NOAA Climate.gov image, based on NOAA Coral Reef Watch data.