The seacoast of Isumi City, Chiba Prefecture, Japan, is one of the northernmost nesting sites of loggerhead sea turtle Carettta caretta in the North Pacific. We observed nesting and hatching events of this species and investigated for asynchronous emergence of hatchlings from 2008 to 2010. In 2008, hatchlings emerged from all nests from July to September, but in 2009 and 2010, most clutches laid in August failed to hatch probably due to low ambient temperature resulting from low atmospheric temperature with insufficient sunshine. In one nest constructed in early July of 2010, hatchling emergence started in early September and completed in late September, 18 days after initial emergence. This extends the previous maximum records of duration of emergence from a single nest by 13 days.