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Several studies have reported fragmentary evidence that climate change is altering the phenology and behavior of honey bees. We compiled records of off-season swarming of the Japanese honey bee (Apis cerana japonica) between autumn and winter to improve our understanding of the impact of climate change on the subspecies’ swarming phenology. Based on a survey of 311 beekeepers, eleven off-season swarming records were collected, with ten of them are from 2020 onward. The beekeepers who reported off-season swarming records had eight to twenty years of beekeeping experience, and they declared that they were witnessing off-season swarming for the first time, suggesting a recent increase. One possible factor contributing to the increase in off-season swarming is the temperature rise, as average autumn and winter temperatures in Japan have been increasing.