A tropical storm made landfall Tuesday near Freeport, Texas, while a hurricane in the Atlantic threatens Bermuda.

By Tuesday night Tropical Storm Imelda was downgraded to a tropical depression, but was bringing heavy rains and potentially life-threatening flash flooding over southeast Texas in the next day or so, the National Hurricane Center said in a 10 p.m. update.

"Although it has weakened, slow-moving Imelda will remain a rainfall/flood threat for at least the next couple of days," the hurricane center said in a forecast discussion.

Houston's police chief warned of a significant potential for flooding and urged people to avoid unnecessary travel.

Imelda is forecast to produce total rainfalls of 6 to 12 inches across the upper coastal region of Texas, which includes Houston and Galveston. The National Weather Service in Houston reported Tuesday night that around 7 inches of rain had fallen in some areas.

Flash flood watches had been issued for areas with a population of around 6 million people, including in Houston and Galveston, the same region that was inundated with catastrophic flooding by Hurricane Harvey in 2017.

At the same time, meteorologists are watching two storms in the Atlantic that have the potential to cause damage in the Caribbean.

Tropical Storm Imelda forms in the Gulf of Mexico on Sept. 17, 2019. NOAA

The National Hurricane Center said that Hurricane Humberto is posing a strong threat to Bermuda. Humberto strengthened into a Category 3 hurricane Tuesday night with maximum sustained winds of 115 mph.

The National Hurricane Center anticipates Humberto's center to pass just to the northwest and north of Bermuda on Wednesday night. Hurricane conditions are expected to reach Bermuda by Wednesday night and continue into early Thursday. The storm could bring between 2 and 4 inches of rain, with maximum amounts of 6 inches. Storm surges and "dangerous breaking waves" could also cause coastal flooding.

Another storm system, dubbed Tropical Depression Ten, was in the Atlantic Ocean and is expected to be a hurricane by the time it approaches the northern Leeward Islands Thursday night and Friday, the hurricane center said.

But the center cautioned that "it is too soon to determine if there will be any direct impacts in the islands."