(NEW YORK) -- Tropical Storm Nicholas is closing in on Texas where a hurricane watch has been issued south of Galveston and schools have been canceled in Houston.
Nicholas, now churning with 60 mph winds, could strengthen to a hurricane when it makes landfall Monday (hurricanes have 74 mph or higher winds).
Heavy rain, flash flooding, dangerous storm surge, isolated tornadoes and gusty winds are expected in Texas and Louisiana.
In Houston, the heaviest rain will come Monday night, and flash flooding is possible.
In Harris County, which encompasses Houston, Judge Lina Hidalgo warned Monday afternoon: "We could get 10 to 15 inches of rain over the next 24 hours or so -- and that would be very, very concerning."
All public health testing and vaccination sites will stop operations in Harris County. Schools in Houston will be closed on Tuesday.
"What I need each resident of this county to do today is to get to where you are going to be by 6 p.m. tonight and stay there," Hidalgo said.
Nicholas is slow moving and will likely remain in Texas from Monday to Wednesday.
Rainfall totals will be the highest around Galveston, where 10 inches are possible.
Storm surge could be as high as 5 feet south of Galveston.
On Tuesday, Nicholas is forecast to bring heavy rain to eastern Texas and into Louisiana. By Wednesday, some of the heavy rain will begin to reach New Orleans.
In Louisiana, where residents are still recovering from devastating hurricanes Laura and Ida, Gov. John Bel Edwards has declared a state of emergency.
The rainfall could be as intense as 2 inches per hour, with a total of 5 inches of rain possible.
“The most severe threat to Louisiana is in the Southwest portion of the state, where recovery from Hurricane Laura and the May flooding is ongoing. In this area heavy rain and flash flooding are possible," the governor said in a statement. "However, it is also likely that all of South Louisiana will see heavy rain this week, including areas recently affected by Hurricane Ida. This tropical storm has the potential to disrupt some power restoration and recovery work currently underway."