World quality silk production surged due to the development of bivoltine breeds driven by innovative breeding programs and extension initiatives. The mulberry silkworm, Bombyxmori L. voltinism is geographically differentiated, with tropical multivoltine exhibiting continuous embryogenesis, while temperate regions host univoltine and bivoltine forms employing diapause. Bivoltine silkworms display a plastic diapause response, modulated by environmental cues. Although multivoltine races are more tolerant of high temperatures, bivoltine races offer better yield potential and produce superior silk quality. However, bivoltine silkworms are highly sensitive to environmental fluctuations, including both biotic and abiotic factors. Temperature, being the critical abiotic factor, profoundly impacts growth and productivity due to their poikilothermic nature. Studies suggest that the optimal temperature for producing high-quality cocoons ranges from 22 to 28 °C. However, sericulture is practiced in regions ranging from tropical to temperate climates, where environmental variations significantly impact economic traits like cocoon weight, shell weight, and shell ratio. Differences in temperature and humidity create distinct rearing conditions across regions. Due to changing climate conditions and their profound impact on lepidopteran insects, silkworm breeders have shifted their focus from solely pursuing high-yielding hybrids to developing thermotolerant, season- and region-specific varieties. This book chapter aims to review the role of environmental factors on various economic traits of bivoltine silkworms, diapause, the development of region- and season-specific silkworms and changes in silkworm breeding strategies, as well as the species’ vulnerability to climate change.