This Coral Bleaching Virtual Stations web page (formerly known as the Tropical Ocean Coral Bleaching Indices web page) is designed by NOAA Coral Reef Watch to provide near-real-time information on thermal stress that induces coral bleaching for 24 selected reef sites around the globe. The information is extracted from near-real-time satellite remotely sensed global sea surface temperature (SST) measurements and derived indices of coral bleaching related thermal stress from 50 km water pixels surrounding or close to these reef sites. The listed information for each reef site includes the reef site name, current thermal stress status, current Degree Heating Week (DHW) value in degree Celsius-weeks ("Current DHW"), historical maximum DHW value and its year of occurrence ("Hist Max DHW"), current SST value in degrees Celsius ("Current SST"), and the maximum monthly mean SST climatology value for that pixel ("Max Month SST"). DHW in a unit of degree Celsius-weeks is a 12-week accumulation, up to the date listed, of SST anomalies that exceed at least one degree Celsius over the maximum monthly mean SST for that pixel. A map showing a particular reef site and its satellite pixel is accessible by clicking on the reef name. The map page also provides links to other coral bleaching monitoring products, including current satellite ocean surface winds, SST time-series, and past Satellite Bleaching Alerts. The regional DHW chart for each site is accessible by clicking on "Current DHW".

The five status levels of thermal stress are defined as No Stress, Bleaching Watch, Bleaching Warning, Bleaching Alert Level 1, and Bleaching Alert Level 2.

These levels are defined in terms of the HotSpot and Degree Heating Weeks (DHW) values at the selected reef sites. When thermal stress is present at a reef site, i.e., current SST exceeds the maximum monthly mean SST, a Bleaching Watch is issued through Coral Reef Watch's Satellite Bleaching Alert (SBA) System. On this page a triangular warning icon is added to that reef site and the status text is displayed in red text. A Bleaching Warning is issued when the current SST reaches 1 degree Celsius over the maximum monthly mean SST. At this point, DHWs begin accumulating and a larger triangular icon is displayed. An accumulation of 4 DHWs triggers a Bleaching Alert Level 1 and the status is displayed in bold red text. At Bleaching Alert Level 1, bleaching is expected at the site within a few weeks of the alert. An accumulation of 8 DHWs triggers a Bleaching Alert Level 2, at which point wide spread bleaching and some coral mortality are likely.

The time of peak bleaching season varies among ocean basins and hemispheres. Generally, the peak season for both the northern Atlantic Ocean and the northern Pacific Ocean is July-September and for both the southern Atlantic Ocean and southern Pacific Ocean is January-March. The peak season for the northern Indian Ocean is April-June and for the southern Indian Ocean is January-April.