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Fox News Weather Center

WATCH: Massive Sinkhole Forms in San Francisco Neighborhood After Soaking Rain

Heavy rainfall inundated the Bay Area through Wednesday, and the rain likely caused the formation of a large sinkhole in San Francisco's Richmond section.

The sinkhole was reported to grow to 20 feet wide by 30 feet in length according to CBS San Francisco.

The drought-plagued region has received welcome rain this week. San Francisco International Airport has received 3.58 inches of rain through Thursday evening. A normal total for the entire month of December is 4.03 inches.

Some locations have received more than 4 inches of rain.

Significant rainfall is a key ingredient as to whether a sinkhole will open because once the water is underground, without proper drainage, it can pool and eat away at soluble materials as previously reported by AccuWeather.com Staff Writer Molly Cochran. Soluble rocks that could potentially lead to sinkhole formation include limestone, gypsum and salt.

Additional rounds of rain will aim at the San Francisco area into the weekend. The pattern looks stormy for the West Coast, northern California in particular, through the middle of December.