Flooding in National City. (Photo courtesy OnScene.TV)

Heavy rains caused widespread roadway flooding across San Diego County Thursday, prompting closures, cautions and detours from Oceanside to National City, authorities said.

In North County, the California Highway Patrol closed the eastbound state Route 78 on-ramp from El Camino Real in Oceanside due to flooding.

CHP also urged drivers to use caution near 8000 Harmony Grove Road, where county crews were clearing small rocks and debris washed onto the roadway; officials said the road could be closed if conditions worsen.

Along the coast, CHP reported flooding where southbound Interstate 5 meets the Sorrento Valley Road/Mira Mesa Boulevard on-ramp, a major connector for commuters.

Additional flooding was reported on southbound I-5 at South Via de la Valle in Del Mar, a key interchange providing access to downtown San Diego and the Del Mar Fairgrounds.

A car caught in a flooded Reynard Street that runs through Mission Hills and Bankers Hill. (Photo by Matt Kroger)

In the South Bay, National City police advised motorists to avoid Mile of Cars Way and Hoover Avenue, which were closed and impassable due to flooding. Detours were in place, with no estimate given for when the roads would reopen.

Meanwhile, Coronado police said the Five Points area, which was closed earlier in the day because of flooding, has since reopened.

Authorities urged drivers to slow down, avoid flooded roads and allow extra travel time as rain continued to move through the region.

City News Service contributed to this article.

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