COLUMBUS, Ohio — Periods of rain and thunderstorms are expected across central Ohio through Sunday, followed by a cooler, unsettled stretch early next week. A Flood Watch is in effect until noon Sunday for locations south of Interstate 70, where pockets of heavy rain could lead to localized flooding. Several counties in southern and southeastern Ohio also have flood advisories or warnings in effect. A frontal boundary moving north is expected to trigger showers and a few thunderstorms overnight Saturday. Columbus temperatures reached about 80 degrees, and elevated humidity could support downpours. On Sunday, a weak low-pressure system will cross the Ohio Valley as a cold front moves through the state. Showers and isolated storms are expected, with the greatest chances in southern Ohio. Rain chances will continue into early next week as the frontal boundary stalls south of the Ohio River and additional disturbances move through from the northwest. The pattern is expected to bring a noticeable cooldown, with daytime highs near 70 degrees and morning lows in the upper 50s. The seasonal shift will become official Tuesday evening at 8:05 p.m. Eastern time, when fall begins. Residents in flood-prone areas should monitor changing conditions, avoid driving through flooded roads and check local alerts before traveling, particularly during periods of heavy rain.