The brown marmorated stink bug, Halyomorpha halys (Stål), is native to eastern 
Asia and is presently invading North America. Little is known about the exposure 
to and effects of winter temperatures in newly invaded regions on H. halys The 
overwintering habitats that this species utilizes vary greatly in their thermal 
buffering capacity. They naturally overwinter in aggregations beneath loose bark 
on trees and in cliff outcroppings, but will also commonly aggregate in 
buildings. Effects of cold temperatures such as mortality and freezing have yet 
to be quantified in the invading population. We report that H. halys is chill 
intolerant (i.e., dies before reaching its freezing point), and that the degree 
of cold tolerance of populations in North America differs by season, sex, and 
acclimation location. The mean winter supercooling point (± SEM) of individuals 
acclimated in Minnesota was -17.06 °C ± 0.13 and in Virginia was -13.90 °C ± 
0.09. By using laboratory assays of lower lethal temperatures and ambient air 
temperature records, we accurately forecasted mortality for field experiments in 
Minnesota and Virginia. Temperature refugia provided by human-built structures 
are likely crucial for overwintering survival during atypically cold winters and 
possibly contribute to the northern geographic range expansion of this 
economically damaging insect in the temperate climates of North America.