LAS VEGAS (KLAS) — Hurricane Hillary strengthened to Category 4 status sustaining 145 mph winds early Friday and prompting local officials to address their preparedness for potential flooding in the Las Vegas valley over the weekend.

According to 8 News Now forecaster Sherry Swensk, the heaviest and most consistent rain was expected on Sunday leading into Monday morning. That precipitation, she said, could lead to flooding.

Hurricane officials said the storm was capable of bringing heavy rainfall to the Southwestern United States that could dump 3 to 6 inches in parts with isolated amounts of up to 10 inches to portions of southern California and southern Nevada, hitting large desert areas unaccustomed to much rain.

On Friday, Clark County officials said they expected a “100-year event” or “1 percent chance storm, that Las Vegas valley flooding infrastructure was designed to handle. Still, officials said they were concerned about outlying areas and the homeless population inhabiting storm drains.

As a reaction to that concern, volunteers from the organization Vegas Stronger turned their attention underground Friday, in an effort to help homeless people living in the city’s flood channels.

Over the weekend, Clark County officials warned of possible widespread flooding conditions. That warning included a list of flood safety tips and ways to prepare in case of an emergency.

While the then-Hurricane Hilary had sustained winds near 130 mph, the storm was downgraded to a Category 1 hurricane overnight on Saturday, according to the National Hurricane Center, before being downgraded again to a tropical storm on Sunday.

On Sunday Clark County Manager Kevin Schiller, and Governor Joe Lombardo declared a State of Emergency for Clark County and all of Nevada due to the impending impact of the storm.

At the same time, the Mohave County Sheriff’s Office issued a GO Evacuation Order for the Temple Bar and Willow Beach areas of Lake Mead National Park, asking everyone in the area to evacuate and head for higher ground.

Sunday evening brought flash flood and high wind warnings as the Las Vegas valley braced for impact from the remnants of Hilary. Local Las Vegas valley roads remained wet into Monday morning, with several power outages impacting around 700 NVEnergy customers.

At approximately 4:45 a.m. on Monday morning, Hilary was downgraded again, this time from tropical storm to post-tropical.

Throughout the event, Mount Charleston received seven inches of rainfall with significant flooding reported, according to the National Weather Service in Las Vegas. On Monday morning there was no working water on the mountain and all residents were under a boil water order. Simultaneusly, flights were being impacted from Las Vegas to California, due to the weather.

The Associated Press contributed to this report.