SAN DIEGO (FOX 5/KUSI) — A Flash Flood Warning for “life threatening” conditions and a rare Tornado Warning were issued by the National Weather Service for parts of San Diego County on Tuesday, as a strong atmospheric river continued to pummel the region with heavy rain.

The Flash Flood Warning was issued just before 10 a.m. for communities stretching between San Diego and Orange counties as the rainfall rate neared 0.75 to one inch per hour with an additional one to two inches possible, according to NWS. It expired at 1 p.m. Tuesday.

Neighborhoods in San Diego County’s northernmost tip, such as Oceanside and Fallbrook, were included in the advisory. A map of the advisory can be found below.

While the warning was in place, NWS said “life threatening” flash flooding could occur, particularly near streams, creeks and other waterways. Low-laying urban areas, highways, streets and underpasses were also likely to see flooding.

Several hours after the Flash Flood Warning was issued, a rare Tornado Warning was issued for a stretch of South Bay and East County just after 11:45 a.m. after a strong thunderstorm capable of producing spiraling was detected by NWS.

“Pea-sized hail” and winds upwards of 40 miles per hour were also said to be possible in communities under the warning, such as Chula Vista, National City, Spring Valley, El Cajon, Santee and Lakeside.

The warning was canceled around 12:30 p.m. According to NWS, the system began to weaken below severe limits before the warning expired, meaning it “no longer appears capable of producing a tornado.”

At this time, it is unknown if any spiraling was reported while the warnings were in place.

Maps of the areas that were impacted by the tornado warning can be found below.

In response to the warning, San Diego State University placed all students under a “Take Cover” alert. All people on campus and in the surrounding areas were encouraged to avoid windows and stay indoors, while protecting from any flying debris.

The rest of San Diego County remains under a Flood Watch through Wednesday as the rain continues. Isolated thunderstorms may also be possible through Tuesday afternoon in inland areas, as well as off the coast.

Rainfall is expected to taper off to a light shower Wednesday afternoon. However, as of Tuesday morning, most of the county has already received upwards of an inch to two inches, while several parts of North County — like Oceanside — saw rainfall that broke single-day records.

Authorities said the flooding also led to at least one death, a migrant who was attempting to cross the U.S. border by swimming through the swollen Tijuana River.

FOX 5/KUSI are tracking the storm. Check back for updates.