MEXICO CITY — Hurricane Rachel has been upgraded to a Category 3 storm off Mexico’s Pacific coast, according to the National Hurricane Center, as northern Mexico and parts of the U.S. Southwest were reeling from flooding and damage from the remnants of Hurricane Polo earlier this week.

The storm, located about 245 miles (390 kilometers) off the southern tip of Baja California, is slowly continuing westward and expected to strengthen in the next day before weakening this weekend.

Rachel’s swells are expected to generate life-threatening surf off Mexico’s coast, the NHC warned. The maximum sustained winds were 120 miles per hour (139 kph) as of Thursday afternoon.

Mexican authorities said Thursday that they remain on alert because of forecasts of very heavy rain in the states of Baja California Sur, Sinaloa, and Jalisco, and the possibility of landslides, rising river levels, overflowing rivers and flooding in low-lying areas.

On Wednesday night, the U.S. Embassy in Mexico warned U.S. citizens in Cabos San Lucas, a popular vacation destination for Americans, of beach and port closures and deadly rip currents.

The Pacific has seen an unusually busy hurricane season, which experts have attributed to El Niño, which has fueled crippling droughts in Mexico and Central America and floods in other parts of the region. In the Pacific, it has resulted in warmer waters and wind patterns that act as fodder for hurricanes. Tropical Storm Nolo continued its northwest approach away from Hawaii on Thursday, though the National Weather Service said it could strengthen into a hurricane by the weekend.

Parts of Texas, Nebraska, Missouri and Iowa were still under flood watch Thursday afternoon as storm remnants continued to batter the region, flooding streets and neighborhoods and setting off water rescues.

Wednesday was the wettest day on record for Lincoln, Nebraska, which received 6.1 inches of rainfall, according to the University of Nebraska-Lincoln Climate Office.

In Omaha, which received 4.7 inches of rain Wednesday, the fire department said it responded to 80 water rescues over a three-hour period ending early Thursday. Some floodwaters reached depths of 8 feet. Schools remained open, but many buses never made it out of flooded parking lots, prompting officials to ask parents to transport their students to school.

More than 20,000 residents in Texas were without power Thursday afternoon, according to PowerOutage.us. Videos posted on social media showed floodwaters in Texas creating waves along Interstate 35 in Denton. The city of San Antonio urged residents to avoid unnecessary travel during periods of heavy rain.

In Chicago, a wastewater treatment and stormwater management utility urged residents to conserve water use to prevent flooding and stormwater backup.

“We encourage everyone to conserve water when possible to create more capacity in our systems,” utility President Kari K. Steele said in a statement Wednesday.

In Kansas, Gov. Laura Kelly issued an emergency proclamation on Wednesday ahead of the storms that allows state resources to assist first responders in hard-hit communities.