Adaptation to local environments involves evolution of ecologically important traits and underlying physiological processes. One challenge in studying the genetic architecture of local adaptation is to achieve high marker density to detect candidate genes in natural populations that often have small blocks of linkage disequilibrium. Here, we used low coverage whole-genome resequencing (lcWGR) to identify genome regions involved in thermal adaptation in wild redband trout Oncorhynchus mykiss gairdneri, a subspecies of rainbow trout that inhabits ecosystems ranging from cold montane forests to high elevation deserts.