Extremely heavy rain moved through the Rochester-Finger Lakes region Thursday morning, prompting the National Weather Service to issue flood warnings for much of the area.

Most locations received roughly an inch of rain by by 10:30 a.m. in many places, though a few locations reported much more. A weather station in Rush, for instance, recorded 2.9 inches of rain since 12 midnight.

A flooding warning issued by the weather service for Ontario and Wayne counties said 2½ inches of rain had flooded numerous homes.

A slightly different flash-flood warning for Monroe County said 2 inches of rain had led to many road closures.

Flash flooding was imminent in roads and low-lying areas, the weather service said. Interstate highways such as I-490, I-390 and the New York State Thruway will be affected, with underpasses especially vulnerable to flooding.

Forecasters cautioned motorists against driving into sections of road covered by standing water.

Creek flooding also is likely, the weather service said. The warning is to remain in place until 12:30 p.m.

Early-morning downpours were blamed for isolated road flooding and several accidents.

A flash-flood watch was in place for Yates, Steuben and other counties to the south and east, and a flood advisory has been issued for northwestern Seneca County, northern Cayuga County and several counties to their east. The weather service said an inch of rain had fallen there in the previous two hours and more was imminent.

The rain, which is expected to continue through Thursday afternoon, could push already-swollen Lake Ontario to new record heights.

The heavy rain could put a damper on the hopes of Lake Ontario shoreline property owners that water levels will go down.

The lake has been above the previous record high water level since May 31, and peaked at its highest point yet on Friday after a modest rainfall on Thursday.

It has declined slightly since then, but likely would go up again after Thursday's rainfall, with a new high-water mark possible.

Rain is expected to let up by early Friday, with sunny skies returning for much of the day.

Rainfall in Rochester was very close to the long-term average for the first half of June, but areas near the east end of Lake Ontario have had nearly double their normal ration of rain in that time.

SORR@Gannett.com