In San Juan County, New Mexico, floodwater entered homes in low-lying areas and pushed sewage into the San Juan River. Emergency crews rescued residents from rooftops, county public information officer Devin Neeley said. The county declared an emergency, and residents in vulnerable areas were told to leave on Thursday.

Neeley described the flooding as unprecedented in living memory. He warned that clear skies in some places did not reflect the danger posed by rising rivers, and said the community expected safety risks and damage to continue through the weekend.

In Farmington, Police Chief Steve Hebbe said Friday that no deaths had been reported so far, but urged people to take the emergency seriously. In southern Utah, Hurricane officials declared an emergency after flooding damaged more than 100 homes and recreational vehicles. The Navajo Nation Police Department reported rescuing 30 people from seven families, while the Hopi Tribe declared an emergency over damage to roads, bridges, homes and other infrastructure.

Colorado Gov. Jared Polis declared disaster emergencies in 11 counties and authorized National Guard assistance with rescue efforts in southwest Colorado. The Archuleta County Sheriff’s Office urged residents to shelter in place Friday morning before issuing an evacuation warning later that day.

The rain began affecting the Four Corners region on Wednesday. National Weather Service meteorologist Kris Sanders said parts of southwest Colorado and southeast Utah received 2 to 4 inches, while some higher elevations in the San Juan Mountains recorded as much as 6 inches. He said the totals set rainfall records and caused creeks, streams and rivers to rise rapidly.

The region’s steep, mountainous terrain can make intense rainfall especially dangerous by funneling water into channels and communities downstream. Sanders said storms of this type can occur at this time of year, and noted that a major flood event affected some of the same areas last year.

Climate scientist Daniel Swain said unusually abundant atmospheric moisture helped fuel the storms. He linked the moisture to record-warm waters off parts of the West Coast, a strong El Niño and a marine heat wave that he said was largely driven by human-caused climate change. Swain said scientists had warned that a developing El Niño could bring extreme precipitation to the Southwest through October.

The flooding follows other severe weather in the Southwest this week, including baseball-sized hail in Arizona and a possible tornado near Heber and Overgaard that injured at least one person. Local officials across the Four Corners urged residents to follow evacuation orders and emergency guidance as more storms remained possible.