The data described here result from coral bleaching surveys across the Hawaiian Archipelago from August 20 to December 7, 2019. The data provide information on live coral cover and the percentage and average severity that was bleached, as well as taxa-specific metrics (live cover and the percentage and severity that was bleached). The data were collected during a multi-institutional effort by the Hawaii Coral Bleaching Collaborative (HCBC) to build a comprehensive dataset of the spatial extent and severity of bleaching in the Hawaiian Archipelago during the peak of the forecasted 2019 coral bleaching event. This dataset is a compilation of data supplied by: NOAA Fisheries Ecosystem Sciences Division (ESD); State of Hawaii Department of Land and Natural Resources (DLNR), Division of Aquatic Resources (DAR); Scripps Institution of Oceanography (SIO), Sandin Lab; Arizona State University (ASU), Asner Lab; National Park Service (NPS), Pacific Island Inventory & Monitoring Network (PACN); Hawaii Institute of Marine Biology (HIMB), Coral Reef Ecology Lab; and The Nature Conservancy (TNC) of Hawaii.

Coral bleaching surveys were conducted at both fixed and random sites using varying methods per institution that included: rapid visual assessments, photoquadrat assessments, and transect-intercept assessments. Metrics that were recorded include live coral cover, the percentage of living coral that was bleached, and the average severity of bleached corals. Surveys conducted in the Main Hawaiian Islands were conducted during shore-based missions, whereas surveys in the Northwestern Hawaiian Islands were performed opportunistically during the regularly scheduled NOAA National Coral Reef Monitoring Program (NCRMP) mission.

Random sites were selected by each institution in their own ways, as follows: - NOAA ESD: A stratified random sampling (StRS) design was used; the StRS method effectively reduces estimate variance through stratification using environmental covariates and by sampling more sites rather than sampling more transects at a site - DAR: Randomly chose sites by covering shorelines at depths from 1-15ft with hard bottom substrate, and aligned transects with shoreline access points - TNC: Sites were randomly selected using ARC-GIS within a polygon bounded by 15' and 50' depth clines and clipped to hard bottom habitat, based on NOAA habitat maps - HIMB: Method described in lineage source - ASU: Sites were selected based on two factors: (1) bleaching reports sent into hawaiicoral.org (ASU, DAR, NOAA website) to locate potential hotspots on the Big Island; and (2) areas not reported as potential coldspots. At each selected "site", randomly selected ___location GPS points constrained only by isobaths of 5, 10, and 15m - PACN: Method described in lineage source