Insect defoliators are important biotic disturbance agents in forest ecosystems. Population fluctuations, i.e., outbreaks, of these insects have scale-dependent impacts; periodic small-scale outbreaks promote fine-scale structural heterogeneity and biodiversity in forests while large-scale outbreaks can alter ecosystem function and fiber supplies. In the pacific coastal temperate rainforest of southeastern Alaska, both the hemlock sawfly (Neodiprion tsugae) and western blackheaded budworm (Acleris gloverana) have recently defoliated extensive tracts of western hemlock (Tsuga heterophylla) forest. We compiled USFS aerial detection survey and historical climate data at a 1 km2 resolution across the temperate rainforest from 1972-2020 and applied machine learning algorithmsto identify spatiotemporal linkages between climate and these two defoliators. Our objective was to investigate how climate patterns drive irruptive defoliation activity in these two species and whether previous hemlock sawfly defoliation alters the likelihood of western blackheaded budworm outbreaks.