The director of the Federal Emergency Management Agency, Brock Long, said the government is expected to conduct a “mass care mission” and predicted that the aftermath of the storm would require FEMA’s involvement for years.

“This disaster’s going to be a landmark event,” Long said.

The latest forecasts showed that 15 to 25 more inches (38 to 63 centimeters) in Texas was possible over the next several days. Rainfall from Harvey could reach up to 50 inches in some spots, making it the highest ever recorded in the state, the National Weather Service announced. Houston has already received more than 20 inches of rain as of Sunday.

Texas Gov. Greg Abbott told “Fox News Sunday” the storm is “bad news growing worse.”

“We’re measuring rain these days not in inches but in feet,” Texas Gov. Greg Abbott told “Fox News Sunday.”

Houston Police Chief Art Acevedo echoed Abbott’s concerns on “Fox & Friends Weekend,” saying the city’s 9-1-1 system has been “overwhelmed” since Harvey struck.

“Do not call 9-1-1 unless it is a life or death situation…[we’re telling people] not to panic,” Acevedo said, adding that “we haven’t seen the worst of it yet.”

Houston residents, attempting to escape the water quickly rising in their homes, were spotted on top of gates outside their homes and on kayaks. Acevedo urged residents not to go to their attics and instead seek refuge on their roofs.

“Reports of people getting into attic to escape floodwater — do not do so unless you have an ax or means to break through onto your roof,” Acevedo wrote on Twitter.

Tom Schlueter had just bought his new black 2017 Mercedes convertible, but it’s now submerged with just 25 miles on it. Schlueter, who stands 6 feet tall and lives in the Galleria area of Houston, told Fox News the water outside his house is up to his chin.

“I’m soaked and freaking out,” he said.

Schlueter and his wife had to be water rescued by the fire department from their home. Their living room, bedroom and kitchen were all at the mercy of Harvey. He walked two blocks to the Granduca Hotel carrying only two pairs of clothes. The hotel, serving as a makeshift shelter for neighbors in need, supplied him with toiletries and other items.

Harris County sheriff’s spokesman Jason Spencer said flooding throughout the county that includes Houston and the region is so widespread that it’s “difficult to pinpoint the worst area.”

“It’s heartbreaking,” Spencer said.

Acevedo said rainwater threatens to bring more flooding into the city in the coming days as it trickles down from other parts of the state.

“[I] cannot emphasize enough how much flooding there is on roadways. You are endangering yourself and our first responders by being out. Stay put,” Acevedo wrote on Twitter earlier.

Meanwhile, Harris County Sheriff Ed Gonzalez and Turner continued urging residents on Twitter to “shelter in place” and stay off rain-swollen roadways.

Gonzalez actively used Twitter overnight Sunday to field assistance for those trapped inside water-soaked homes, attics and vehicles. Those appealing for assistance or being steered to help via Gonzalez’s Twitter feed included a person suffering “cardiac-arrest,” and a woman who posted: “I have 2 children with me and the water is swallowing us up. Please send help.”

Gonzalez at one point appealed for calm and patience, saying officials were “trying to make it to everyone as best we can.”

The airfield was closed at William P. Hobby Airport Saturday night due to standing water on the runways, according to FOX26. Hundreds of flights were canceled and travelers were left stranded in the area.

Harvey made landfall as a Category 4 hurricane late Friday night, but downgraded to a tropical storm by Saturday. The hurricane center said in its 4 a.m. Sunday update that the tropical storm has maximum sustained winds of 45 mph and remains stationary about 45 miles northwest of Victoria, Texas.

At least one person died due to the flooding, Houston Fire Department’s Sheldra Brigham said. Paramedics found the individual in a vehicle just before 10 p.m. A doctor, a passerby who stopped to help, was already at the scene and pronounced the person dead. A second person was confirmed dead in a house fire as the hurricane came ashore Friday night. Aransas County Judge C.H. “Burt” Mills Jr. told the Austin American-Statesman that 12 to 14 other people were injured.

Trump announced on Sunday he will be heading to Texas as soon as possible and praised emergency crews and government officials for search and rescue efforts.

“I will be going to Texas as soon as that trip can be made without causing disruption. The focus must be life and safety,” Trump tweeted.

Trump said on Saturday he was “closely monitoring” the storm from Camp David.

Abbott said Trump’s response to the storm was “extremely professional, very helpful” and offered any resources the governor needed. He added it’s still unclear what amount of money will be needed for storm damage repairs, but estimated to be “billions of dollars.”

New York City Mayor Bill de Blasio also said on Twitter the city will be sending 120 emergency personnel to Texas to assist with the storm’s aftermath. The Red Cross opened 21 shelters to hold about 1,450 people.

The Coast Guard, which received more than 300 requests for help, deployed five helicopters and asked for additional aircraft from New Orleans.